Measurement of polarization amplitudes and CP asymmetries in B⁰ → Φk *(892)⁰

JHEP05(2014)069

Published for SISSA by Springer

Received: March 13, 2014 Accepted: April 17, 2014 Published: May 16, 2014

Measurement of polarization amplitudes and CP

asymmetries in B

0

→ φK

∗

(892)

0

The LHCb collaboration

E-mail: dlambert@cern.ch

Abstract: An angular analysis of the decay B0 → φK∗(892)0 is reported based on a pp collision data sample, corresponding to an integrated luminosity of 1.0 fb−1, collected at a centre-of-mass energy of√s= 7 TeV with the LHCb detector. The P-wave amplitudes and phases are measured with a greater precision than by previous experiments, and confirm about equal amounts of longitudinal and transverse polarization. The S-wave K+_π− _and

K+K− contributions are taken into account and found to be significant. A comparison of the B0 _{→ φK}∗₍₈₉₂₎0 _{and B}0 _{→ φK}∗₍₈₉₂₎0 _{results shows no evidence for direct CP}

violation in the rate asymmetry, in the triple-product asymmetries or in the polarization amplitudes and phases.

Keywords: CP violation, Hadron-Hadron Scattering, Polarization, B physics, Flavour Changing Neutral Currents

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Contents 1 Introduction 1 2 Analysis strategy 2 2.1 Angular analysis 3 2.2 Mass distributions 4 2.3 Triple-product asymmetries 5

3 Detector and dataset 6

4 Event selection 7

5 K+K−K+π− mass model 8

6 Angular fit 9

7 Angular analysis results 10

8 Direct CP rate asymmetry 12

9 Conclusions 15

The LHCb collaboration 19

1 Introduction

The decay B0_{→ φK}∗0_,1 _{has a branching fraction of (9.8± 0.6) × 10}−6 _{[1]. In the Standard}

Model it proceeds mainly via the gluonic penguin diagram shown in figure 1. Studies of observables related to CP violation in this decay probe contributions from physics beyond the Standard Model in the penguin loop [2–4]. The decay was first observed by the CLEO collaboration [5]. Subsequently, branching fraction measurements and angular analyses have been reported by the BaBar and Belle collaborations [6–11].

The decay involves a spin-0 B-meson decaying into two spin-1 vector mesons (B → V V). Due to angular momentum conservation there are only three independent configura-tions of the final-state spin vectors, a longitudinal component where in the B0 _{rest frame}

both resonances are polarized in their direction of motion, and two transverse components with collinear and orthogonal polarizations. Angular analyses have shown that the longi-tudinal and transverse components in this decay have roughly equal amplitudes. Similar

1_{In this paper K}∗0

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φ K∗0 B0 ¯b d s ¯ s ¯ s d W+ ¯ t

Figure 1. Leading Feynman diagram for the B0

→ φK∗0 _decay.

results are seen in other B_{→ V V penguin transitions [}12–15]. This is in contrast to tree-level decays such as B0 _{→ ρ}+_ρ−_{, where the V − A nature of the weak interaction causes}

the longitudinal component to dominate. The different behaviour of tree and penguin de-cays has attracted much theoretical attention, with several explanations proposed such as large contributions from penguin annihilation effects [16] or final-state interactions [17,18]. More recent calculations based on QCD factorization [19,20] are consistent with the data, although with significant uncertainties.

In this paper, measurements of the polarization amplitudes, phases, CP asymmetries and product asymmetries are presented. In the Standard Model the CP and triple-product asymmetries are expected to be small and were found to be consistent with zero by previous experiments [6–10]. The studies reported here are performed using pp collision data, corresponding to an integrated luminosity of 1.0 fb−1, collected at a centre-of-mass energy of √s= 7 TeV with the LHCb detector.

2 Analysis strategy

In this analysis the B0_{→ φK}∗0 _{decay is studied, where the φ and K}∗0 _{mesons decay to}

K+K− and K+_π−_{, respectively (the study of the charge conjugate B}0 _{mode is implicitly}

assumed in this paper). Angular momentum conservation, for this pseudoscalar to vector-vector transition, allows three possible helicity configurations of the vector-vector-meson pair, with amplitudes denoted H+1, H−1 and H0. These can be written as a longitudinal polarization,

A0, and two transverse polarizations, A⊥ and Ak,

A0 = H0 , A⊥= H+1− H−1 √ 2 and Ak = H+1+ H−1 √ 2 . (2.1)

In addition to the dominant vector-vector (P-wave) amplitudes, there are contributions where either the K+_K− _{or K}+_π− _{pairs are produced in a spin-0 (S-wave) state. These}

amplitudes are denoted AKK

S and AKπS , respectively. Only the relative phases of the

am-plitudes are physical observables. A phase convention is chosen such that A0 is real. The

remaining amplitudes have magnitudes and relative phases defined as

Ak =|Ak|eiδk , A⊥=|A⊥|eiδ⊥ , AKπS =|AKπS |eiδ

Kπ

S and AKK

S =|AKKS |eiδ

KK

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Figure 2. The helicity angles θ1, θ2, Φ for the B0→ φK∗0 decay.

To determine these quantities, an analysis of the angular distributions and invariant masses of the decay products is performed. It is assumed that the contribution from B0 _→

K+K−K+π−, where both the K+_K− _{and K}+_π− _{are non-resonant, is negligible.}

In the following sections the key elements of the analysis are discussed. First, the con-ventions used in the angular analysis are defined together with the form of the differential cross-section. Next, the parameterization of the K+_π− _{and K}+_K− _{mass distributions is}

discussed. Finally, the triple-product asymmetries that can be derived from the angular variables are defined.

2.1 Angular analysis

The angular analysis is performed in terms of three helicity angles (θ1, θ2,Φ), as depicted in

figure2. The angle θ1 is defined as the angle between the K+ direction and the reverse of

the B0 _{direction in the K}∗0_{rest frame. Similarly, θ}

2is the angle between the K+direction

and the reverse of the B0 _{direction in the φ rest frame. The angle Φ is the angle between}

the decay planes of the φ and K∗0 _{mesons in the B}0 _{rest frame.}

The flavour of the decaying B0 _{meson is determined by the charge of the kaon from the}

K∗0decay. To determine the polarization amplitudes, the B0 _{and B}0_{decays are combined.}

For the study of CP asymmetries, the B0 _{and B}0 _{decays are separated.}

Taking into account both the P- and S-wave contributions and their interference, the differential decay rate [8] is given by the sum of the fifteen terms given in table1,

d5Γ = 9 8π 15 X i=1 hi fi(θ1, θ2,Φ)Mi(mKπ, mKK)dΩ(KKKπ) . (2.3)

The hi factors are combinations of the amplitudes, fi are functions of the helicity angles,

Mi are functions of the invariant mass of the intermediate resonances and dΩ(KKKπ) is

a four-body phase-space factor,

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i hi fi(θ1, θ2,Φ) Mi(mKπ, mKK)

1 |A0|2 cos θ21cos θ22 |M1Kπ(mKπ)|2|M1KK(mKK)|2

2 |Ak|2 14sin θ12sin θ22(1 + cos(2Φ)) |M1Kπ(mKπ)|2|M1KK(mKK)|2

3 |A⊥|2 14sin θ12sin θ22(1− cos(2Φ)) |M1Kπ(mKπ)|2|M1KK(mKK)|2

4 |A⊥||A∗k|ei(δ⊥

−δk) ₋1

2sin θ21sin θ22sin(2Φ) |M1Kπ(mKπ)|2|M1KK(mKK)|2

5 |Ak||A∗0|eiδk

√

2 cos θ1sin θ1cos θ2sin θ2cos Φ |M1Kπ(mKπ)|2|M1KK(mKK)|2

6 |A⊥||A∗0|eiδ⊥ −

√

2 cos θ1sin θ1cos θ2sin θ2sin Φ |M1Kπ(mKπ)|2|M1KK(mKK)|2

7 |AKπ S |2 13cos θ22 |M0Kπ(mKπ)|2|M1KK(mKK)|2 8 |Ak||A∗KπS |ei(δk −δKπ S ) √ 6

3 sin θ1cos θ2sin θ2cos Φ |M1KK(mKK)|2M1Kπ(mKπ)M0∗Kπ(mKπ)

9 |A⊥||A∗KπS |ei(δ⊥−δ

Kπ

S ) −

√ 6

3 sin θ1cos θ2sin θ2sin Φ |M

KK 1 (mKK)|2M1Kπ(mKπ)M0∗Kπ(mKπ) 10 |A0||A∗KπS |e−iδ Kπ S √2 3cos θ1cos θ 2 2 |M1KK(mKK)|2M1Kπ(mKπ)M0∗Kπ(mKπ) 11 |AKK S |2 13cos θ21 |M0KK(mKK)|2|M1Kπ(mKπ)|2 12 |Ak||A∗KKS |ei(δk−δ KK S ) √ 6

3 sin θ1cos θ1sin θ2cos Φ |M1Kπ(mKπ)|2M1KK(mKK)M0∗KK(mKK)

13 |A⊥||A∗KKS |ei(δ⊥

−δKK S ) −

√ 6

3 sin θ1cos θ1sin θ2sin Φ |M1Kπ(mKπ)|2M1KK(mKK)M0∗KK(mKK)

14 |A0||A∗KKS |e−iδ KK S √2 3cos θ 2 1cos θ2 |M1Kπ(mKπ)|2M1KK(mKK)M0∗KK(mKK) 15 |AKπ S ||A∗KKS |ei(δ Kπ S −δKKS ) 2 3cos θ1cos θ2 M1KK(mKK)M0Kπ(mKπ)M0∗KK(mKK)M1∗Kπ(mKπ)

Table 1. Definition of the hi, fi and Mi terms in eq. (2.3). Note that the P-wave interference

terms i = 4 and i = 6 take the imaginary parts of A⊥A∗_k and A⊥A∗0, while i = 5 takes the real

part of AkA∗0. Similarly the S-wave interference terms i = 9 and i = 13 take the imaginary parts of

A⊥A∗SM1M0∗, and the terms i = 8, 10, 12, 14 take the real parts of AkA∗SM1M0∗ and A0A∗SM1M0∗.

where qA is the momentum of the daughter particles in the mother’s (A = B0, φ, K∗0)

centre-of-mass system.

The differential decay rate for B0_{→ φK}∗0 is obtained by defining the angles using the charge conjugate final-state particles and multiplying the interference terms f4, f6, f9, f13

by _{−1. To allow for direct CP violation, the amplitudes A}j are replaced by Aj, for j =

0,_{k, ⊥, S. The rate is normalized separately for the B}0 and B0 _{decays such that the P- and}

S-wave fractions are

FP=|A0|2+|Ak|2+|A⊥|2 , FS=|AKπS |2+|ASKK|2 , FP+ FS = 1 , (2.5) and FP=|A0|2+|Ak|2+|A⊥|2, FS=|A Kπ S |2+|A KK S |2 , FP+ FS= 1 . (2.6)

In addition, a convention is adopted such that the phases δKπ

S and δSKK are defined as the

difference between the P- and S-wave phases at the K∗0 and φ meson poles, respectively. 2.2 Mass distributions

The differential decay width depends on the invariant masses of the K+_π−_{and K}+_K−

sys-tems, denoted mKπ and mKK, respectively. The P-wave K+π−amplitude is parameterized

using a relativistic spin-1 Breit-Wigner resonance function,

M₁Kπ(mKπ) = mKπ qK∗ mK₀ ∗ΓKπ 1 (mKπ) (mK∗ 0 )2− m2Kπ− imK ∗ 0 ΓKπ1 (mKπ) , (2.7)

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where mK∗

0 = 895.81 MeV/c2 [1] is the K∗0 mass. The mass-dependent width is given by

ΓKπ₁ (mKπ) = ΓK ∗ 0 mK₀ ∗ mKπ 1 + r2_q2 0 1 + r2_q2 K∗  qK∗ q0 3 , (2.8)

where q0is the value of qK∗at mK ∗

0 , r = 3.4 ~c/GeV [21] is the interaction radius and ΓK

∗

0 =

47.4 MeV/c2 _{is the natural width of the K}∗0 _{meson [1]. The P-wave K}+_K− _amplitude,

denoted MKK

1 (mKK), is modelled in a similar way using the values mφ0 = 1019.455 MeV/c2

and Γφ₀ = 4.26 MeV/c2_{[1]. In the case of the φ meson the natural width is comparable to the}

detector resolution of 1.2 MeV/c2_{, which is accounted for by convolving the Breit-Wigner}

with a Gaussian function.

As the K∗0is a relatively broad resonance, the S-wave component in the K+_π−_system,

denoted MKπ

0 (mKπ), needs careful treatment. In this analysis the approach described in

ref. [8] is followed, which makes use of the LASS parameterization [21]. This takes into account an L = 0 K₀∗(1430) contribution together with a non-resonant amplitude. The values used for the LASS parameterization are taken from ref. [8].

Finally, an S-wave in the K+_K−_{system is considered. This is described by the Flatt´e}

parameterization of the f0(980) resonance [22],

M₀KK(mKK) = 1 m2_f 0 − m 2 KK− imf0(gππρππ+ gKKρKK) , (2.9)

where the gKK,ππ are partial decay widths and the ρKK,ππ are phase-space factors. The

values mf0 = 939 MeV/c

2_{, g}

ππ = 199 MeV/c2 and gKK/gππ = 3.0 were measured in ref. [23].

The Flatt´e distribution is convolved with a Gaussian function to account for the detector resolution. Other approaches to modelling the mass distributions for both the K+_π− _and

K+K− S-wave are considered as part of the systematic uncertainty determination. 2.3 Triple-product asymmetries

The amplitudes and phases can be used to calculate triple-product asymmetries [2,4,24]. Nonzero tripleproduct asymmetries arise either due to a T violating phase or a CP -conserving phase and final-state interactions. Assuming CP T symmetry, a T -violating phase, which is a true asymmetry, implies that CP is violated.

For the P-wave decay, two triple-product asymmetries are calculated from the results of the angular analysis [4],

A1_T = Γ(sθ1θ2sin Φ > 0)− Γ(sθ1θ2sin Φ < 0)

Γ(sθ1θ2sin Φ > 0) + Γ(sθ1θ2sin Φ < 0)

and A2_T = Γ(sin 2Φ > 0)− Γ(sin 2Φ < 0) Γ(sin 2Φ > 0) + Γ(sin 2Φ < 0) ,

(2.10) where sθ1θ2 = sign(cos θ1cos θ2). These asymmetries can be rewritten in terms of the

interference terms between the amplitudes [4], h4 and h6 in table1,

A1_T =₋4 πIm(A⊥A ∗ 0) and A2T =− 2√2 π Im(A⊥A ∗ k) . (2.11)

Since the decay products identify the flavour at decay, the data can be separated into B0

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a determination of the true asymmetries, Ak

T(true) = (AkT + A k

T)/2, and so called fake

asymmetries, Ak

T(fake) = (AkT − A k

T)/2, where k = 1, 2. In the Standard Model the value

of Ak

T(true) is predicted to be zero and any deviation from this would indicate physics

beyond the Standard Model. Non-zero values for Ak

T(fake) reflect the importance of strong

final-state phases [4].

The S-wave contributions allow two additional triple-product asymmetries to be de-fined from h9 and h13 in table1,

A3_T = Γ(sθ1sin Φ > 0)− Γ(sθ1sin Φ < 0) Γ(sθ1sin Φ > 0) + Γ(sθ1sin Φ < 0) =₋r 3 2 Z |M1KK(mKK)|2Im(A⊥A∗KπS M1Kπ(mKπ)M0∗Kπ(mKπ))dmKKdmKπ, (2.12) and A4_T = Γ(sθ2sin Φ > 0)− Γ(sθ2sin Φ < 0) Γ(sθ2sin Φ > 0) + Γ(sθ2sin Φ < 0) =−r 3 2 Z |MKπ 1 (mKπ)|2Im(A⊥A∗KKS M1KK(mKK)M0∗KK(mKK))dmKKdmKπ , (2.13)

where sθi = sign(cos θi) for i = 1, 2.

3 Detector and dataset

The LHCb detector [25] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks. The detector includes a high-precision tracking system consisting of a silicon-strip vertex detector sur-rounding the pp interaction region, a large-area silicon-strip detector located upstream of a dipole magnet with a bending power of about 4 Tm, and three stations of silicon-strip detectors and straw drift tubes placed downstream. The polarity of the dipole magnet is reversed at intervals corresponding to roughly 0.1 fb−1 of collected data, in order to minimize systematic uncertainties associated with detector asymmetries. The combined tracking system provides a momentum measurement with relative uncertainty that varies from 0.4 % at 5 GeV/c to 0.6 % at 100 GeV/c, and impact parameter resolution of 20 µm for tracks with high transverse momentum (pT). Charged hadrons are identified using two

ring-imaging Cherenkov detectors [26]. Photon, electron and hadron candidates are iden-tified by a calorimeter system consisting of scintillating-pad and preshower detectors, an electromagnetic calorimeter and a hadronic calorimeter. Muons are identified by a system composed of alternating layers of iron and multiwire proportional chambers.

The trigger [27] consists of a hardware stage, based on information from the calorimeter and muon systems, followed by a software stage, which applies a full event reconstruction. In this analysis two categories of events that pass the hardware trigger stage are considered: those where the signal b-hadron products are used in the trigger decision (TOS) and those

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where the trigger decision is caused by other activity in the event (TIS) [27]. The software

trigger requires a three-track secondary vertex with large transverse momenta of the tracks and a significant displacement from the primary pp interaction vertices (PVs). At least one track should have pT >1.7 GeV/c and χ2IP with respect to any primary interaction greater

than 16, where χ2

IP is defined as the difference in χ2 of a given PV reconstructed with and

without the considered track. A multivariate algorithm [28] is used for the identification of secondary vertices consistent with the decay of a b hadron.

Simulated data samples are used to correct for the detector acceptance and response. In the simulation, pp collisions are generated using Pythia 6.4 [29] with a specific LHCb configuration [30]. Decays of hadronic particles are described by EvtGen [31], in which final-state radiation is generated using Photos [32]. The interaction of the generated particles with the detector and its response are implemented using the Geant4 toolkit [33,

34] as described in ref. [35].

4 Event selection

The selection of events is divided into two parts. In the first step a loose selection is per-formed that retains the majority of signal events, whilst reducing the background by a large fraction. Following this, a multivariate method is used to further reduce the background.

The selection starts from well reconstructed charged particles with a pT >500 MeV/c

that traverse the entire spectrometer. Fake tracks, not associated to actual charged parti-cles, are suppressed using the output of a neural network trained to discriminate between these and real particles [36]. Further background suppression is achieved by exploiting the fact that the products of b-hadron decays have a large impact parameter (IP) with respect to the nearest PV. The IP of each track with respect to any primary vertex is required to have a χ2

IP>9.

To select well-identified pions and kaons, the difference in the logarithms of the likeli-hood of the kaon hypothesis relative to the pion hypothesis (DLLKπ) is provided using

infor-mation from the ring-imaging Cherenkov detectors. The kaons that form the φ_{→ K}+_K−

candidate are required to have DLLKπ > 0. To reduce background from π+π− pairs, a

tighter requirement, DLLKπ >2, is applied to the kaon in the K+π− pair. For the pion in

the K+_π− _{pair the requirement is DLL}

Kπ <0.

The resulting charged particles are combined to form φ and K∗0 meson candidates. The invariant mass of the K+_K− _(K+_π−_{) pair is required to be within}

±15 MeV/c2

(_{±150 MeV/c}2_{) of the known mass of the φ (K}∗0_{) meson [1]. Finally, the p}

T of the φ

and K∗0 mesons should both be greater than 900 MeV/c, and the fit of their two-track vertices should have a χ2_<9.

Candidate B0 _{meson decays with K}+_K−_K+_π− _{invariant mass in the range 5150 <}

mKKKπ <5600 MeV/c2 are formed from pairs of selected φ and K∗0meson candidates. A

fit is made requiring all four final-state particles to originate from a common vertex and the χ2per degree of freedom of this fit is required to be less than 15. To remove B0

s → φφ decays

where a kaon has been incorrectly identified as a pion, the invariant mass of the K+_π−

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is within _{±15 MeV/c}2 _{of the known φ mass, the candidate is rejected. Finally, the decay}

vertex of the B0 _{meson candidate is required to be displaced from the nearest PV, with}

a flight distance significance of more than 5 standard deviations, and the B0 _momentum

vector is required to point back towards the PV with an impact parameter less than 0.3 mm and χ2

IP <5.

Further background suppression is achieved using a geometric likelihood (GL) method [15, 37, 38]. The GL is trained using a sample of simulated B0 _{→ φK}∗0 _signal

events together with background events selected from the upper mass sideband of the B0

meson, mKKKπ > 5413 MeV/c2, and the φ mass sidebands, |mKK − mφ0| > 15 MeV/c2.

These sidebands are not used in the subsequent analysis. Six discriminating variables are input to the GL: the IP of the B0 _{candidate with respect to the PV, the distance of closest}

approach of the φ and K∗0 _{meson candidate trajectories, the lifetime of the B}0 _candidate,

the transverse momentum of the B0 _{candidate, the minimum χ}2

IP of the K+K

− _{pair and}

the minimum χ2

IP of the K+π

−_{pair. As a figure of merit the ratio S/}√_{S+ B is considered,}

where S and B are the yields of signal and background events in the training samples, scaled to match the observed signal and background yields in the data. The maximum value for the figure of merit is found to be 24.6 for GL > 0.1, with signal and background efficiencies of 90 % and 21 %, respectively, compared to the selection performed without the GL. This reduces the sample size for the final analysis to 1852 candidates.

5 K+K−K+π− mass model

The signal yield is determined by an unbinned maximum likelihood fit to the K+_K−_K+_π−

invariant mass distribution. The selected mass range is chosen to avoid modelling partially reconstructed B decays with a missing hadron or photon. In the fit the signal invariant mass distribution is modelled as the sum of a Crystal Ball function [39] and a wider Gaussian function with a common mean. The width and fraction of the Gaussian function are fixed to values obtained using simulated events. A component is also included to account for the small contribution from the decay B0_{s→ φK}∗0 _{[38]. The shape parameters for this}

component are in common with the B0 _{signal shape and the relative position of the B}0 s

signal with respect to the B0 _{signal is fixed using the known mass difference between B}0

and B0

s mesons [1]. The invariant mass distribution is shown in figure3, together with the

result of the fit, from which a yield of 1655± 42 B0 _{signal candidates is found.}

After the selection the background is mainly combinatorial and is modelled by an exponential. Background from B0

s → φφ decays, with one of the kaons misidentified as

a pion is reduced by the veto applied in the selection. The number of candidates from this source is estimated to be 6 events using simulation. These are distributed across the K+K−K+π− mass range, and are considered negligible in the fit. A potential background from B0 _{→ D}+

sK−(Ds+ → φπ+) decays, which would peak in the signal region, is also

found to be negligible. Possible background from the yet unobserved decay Λ0

b → φpK −

JHEP05(2014)069

] 2 c [MeV/ π KKK m 5200 5300 5400 5500 5600 ) 2 c Candidates / ( 10 MeV/ 1 10 2 10 3 10 LHCb

Figure 3. Invariant mass distribution for selected K+_K−_K+_π− _{candidates. A fit to the model}

described in the text is superimposed (red solid line). The signal contribution is shown as the blue dotted line. The contribution from combinatorial background is shown in green (dotted line). A contribution from B0s→ φK∗0 (purple dot-dashed line) decays is visible around the known Bs0

meson mass.

6 Angular fit

The physics parameters of interest for this analysis are defined in table 2. They include the polarization amplitudes, phases and amplitude differences between B0 _{and B}0 _decays

from which the triple-product asymmetries are calculated.

The correlation between the fit variables and mKKKπ is found to be less than

3 %. Therefore, the background can be subtracted using the sPlot method [40], with m_K+_K−_K+_π− as the discriminating variable. The results of the invariant mass fit discussed

in section 5 are used to give each candidate a signal weight, Wn, which is a function

of mK+_K−_K+_π−. The weight is used to subtract the background contributions from the

distributions of the decay angles and intermediate resonance masses, which are fit using a signal-only likelihood that is a function of θ1, θ2,Φ, mKπ and mKK. The angular fit

minimizes the negative log likelihood summed over the n selected candidates

− lnL = −αX

n

WnlnSn, (6.1)

where α =P

nWn/PnWn2 is a normalization factor that includes the effect of the weights

in the determination of the uncertainties [41, 42], and S is the signal probability density function (eq. (2.3)) convolved with the detector acceptance.

The acceptance of the detector is not uniform as a function of the decay angle of the K+π− system (θ1) and the K+π− invariant mass. This is due to the 500 MeV/c criterion

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] 2 c [MeV/ π K m 800 900 1000 Acceptance 0 0.5 1 TOS Not TOS Simulation LHCb _(a) ] 2 c [MeV/ KK m 1010 1020 1030 Acceptance 0 0.5 1 TOS Not TOS Simulation LHCb _(b) 1 θ cos -1 -0.5 0 0.5 1 Acceptance 0 0.5 1 TOS Not TOS Simulation LHCb _(c) 2 θ cos -1 -0.5 0 0.5 1 Acceptance 0 0.5 1 TOS Not TOS Simulation LHCb _(d) [rad] φ 0 1 2 3 4 5 6 Acceptance 0 0.5 1 TOS Not TOS Simulation LHCb _(e)

Figure 4. Binned projections of the detector acceptance for (a) mKπ, (b) mKK , (c) cos θ1, (d)

cos θ2 and (e) Φ. The acceptance for the TOS (filled crosses) and not TOS (open squares) are

shown on each plot.

relatively uniform as a function of the decay angles θ2 and Φ, and the invariant mass of

the K+_K− _system.

The detector acceptance is modelled using a four-dimensional function that depends on the three decay angles and the K+_π− _{invariant mass. The shape of this function is}

obtained from simulated data. As the quantities relating to the pT of the decay products

are used in the first-level hardware based trigger, the acceptance is different for candidates that have a TIS or TOS decision at the hardware trigger stage [27]. Consequently, the trigger acceptance is calculated and corrected separately for the two categories. The 17 % of candidates that fall in the overlap between the two categories are treated as TOS, and the remaining TIS candidates are labelled ‘not TOS’. The projections of the acceptance are shown in figure4. In the subsequent analysis the data set is divided into the two categories and a simultaneous fit is performed.

7 Angular analysis results

Figure 5 shows the data distribution for the intermediate resonance masses and helicity angles with the projections of the best fit overlaid. The goodness of fit is estimated using a point-to-point dissimilarity test [43], the corresponding p-value is 0.64.

The fit results are listed in table2. The value of fLreturned by the fit is close to 0.5,

S-JHEP05(2014)069

] 2 c [MeV/ π K m 800 900 1000 ) 2 c Candidates / ( 10 MeV/ 0 20 40 60 80 100 120 140 160 180 200 220 240 Data Total P-wave KK S-wave S-wave π K LHCb (a) ] 2 c [MeV/ KK m 1010 1020 1030 ) 2 c Candidates / ( 1 MeV/ 0 20 40 60 80 100 120 140 160 180 200 220 LHCb (b) 1 θ cos -1 -0.5 0 0.5 1 Candidates / 0.2 0 50 100 150 200 250 300 _{LHCb (c)} 2 θ cos -1 -0.5 0 0.5 1 Candidates / 0.2 0 50 100 150 200 250 LHCb (d) [rad] Φ 0 2 4 6 Candidates / ( 0.628 rad ) 0 20 40 60 80 100 120 140 160 180 200 220 240 LHCb (e)

Figure 5. Data distribution for the helicity angles and of the intermediate resonance masses: (a) mKπand (b) mKK, (c) cos θ1, (d) cos θ2and (e) Φ. The background has been subtracted using the

sPlot technique. The results of the fit are superimposed.

wave contributions are found in both the K+_π−_{and K}+_K−_{systems. The CP asymmetries}

in both the amplitudes and the phases are consistent with zero.

Using eqs. (2.11)–(2.13), the values for the triple-product asymmetries are derived from the measured parameters and given in table 3. The true asymmetries are consistent with zero, showing no evidence for physics beyond the Standard Model. In contrast, all but one of the fake asymmetries are significantly different from zero, indicating the presence of final-state interactions.

The systematic uncertainties on the measured amplitudes, phases and triple-product asymmetries are summarized in table4. The largest systematic uncertainties on the results of the angular analysis arise from the understanding of the detector acceptance. The

JHEP05(2014)069

angular acceptance function is determined from simulated events as described in section 6.

An uncertainty, labelled ‘Acceptance’ in the table, is assigned to account for the limited size of the simulation sample used. This is estimated using pseudo-experiments with a simplified simulation.

A difference is observed in the kinematic distributions of the final-state particles be-tween data and simulation. This is attributed to the S-wave components, which are not included in the simulation. To account for this, the simulated events are reweighted to match the signal distributions as expected from the best estimate of the physics param-eters from data (including the S-wave). In addition, the events are reweighted to match the observed distributions of the B0 _{candidate and final-state particle transverse momenta.}

The reweighting is done separately for the two trigger categories and the nominal results are recalculated using the reweighted simulation to determine the angular acceptance. The difference between the weighted and unweighted results is taken as a systematic uncertainty (labelled ‘Data/MC’ in the table).

A further uncertainty arises from the K+_K−_K+_π− _{mass model used to determine the}

signal weights for the angular analysis. The fit procedure is repeated using different signal and background models. For the signal component a double Gaussian model is used instead of the sum of a Gaussian and a Crystal Ball function. Similarly, the influence of background modelling is probed using a first-order polynomial instead of an exponential function. Other changes to the background model are related to the possible presence of additional backgrounds. A possible small contribution from misidentified Λb → pK−K+K− and

Λb → pπ−K+K+ decays is added and the fit repeated. Finally, the lower bound of the

fit range is varied and the contribution from partially reconstructed B decays modelled. The largest difference compared to the central values is assigned as an estimate of the systematic uncertainty (labelled ‘Mass model’ in the table).

Alternative models of the S-wave contributions in both the K+_K−_{and K}+_π− _system

are considered. The default fit uses the LASS parameterization to model the K+_π−_S-wave.

As variations of this, both a pure phase-space model and a spin-0 relativistic Breit-Wigner with mean and width of the K∗

0(1430) resonance are considered [1]. For the K+K−

S-wave a pure phase-space model is tried in place of the Flatt´e parameterization. The largest observed deviation from the nominal fit is taken as a systematic uncertainty (column labelled ‘S-wave’ in the table).

Various consistency checks of the results are made. As a cross-check candidates that are in the overlap between the trigger categories are treated as TIS for the angular correction in the fit rather than TOS. The dataset is also divided according to the magnetic field polarity. The results obtained in these studies are consistent with the nominal results and no additional uncertainty is assigned.

8 Direct CP rate asymmetry

The raw measurement of the rate asymmetry is obtained from

A= N(B

0

→ φK∗0)− N(B0_{→ φK}∗0₎

JHEP05(2014)069

Parameter Definition Fitted value

fL 0.5(|A0|2/FP+|A0|2/FP) 0.497± 0.019 ± 0.015 f⊥ 0.5(|A⊥|2/FP+|A⊥|2/FP) 0.221± 0.016 ± 0.013 fS(Kπ) 0.5(|AKπS |2+|A Kπ S |2) 0.143± 0.013 ± 0.012 fS(KK) 0.5(|AKKS |2+|A KK S |2) 0.122± 0.013 ± 0.008 δ⊥ 0.5(arg A⊥+ arg A⊥) 2.633± 0.062 ± 0.037 δk 0.5(arg Ak+ arg Ak) 2.562± 0.069 ± 0.040 δS(Kπ) 0.5(arg AKπS + arg A Kπ S ) 2.222± 0.063 ± 0.081 δS(KK) 0.5(arg AKK_S + arg A KK S ) 2.481± 0.072 ± 0.048 ACP 0 (|A0|2/FP− |A0|2/FP)/(|A0|2/FP+|A0|2/FP) −0.003 ± 0.038 ± 0.005 ACP ⊥ (|A⊥|2/FP− |A⊥|2/FP)/(|A⊥|2/FP+|A⊥|2/FP) +0.047± 0.074 ± 0.009 AS(Kπ)CP (|AKπ_S |2− |A Kπ S |2)/(|AKπS | 2₊ |AKπS |2) +0.073± 0.091 ± 0.035 AS(KK)CP (|AKK_S |2− |A KK S |2)/(|AKKS | 2₊ |AKKS |2) −0.209 ± 0.105 ± 0.012 δ_⊥CP 0.5(arg A⊥− arg A⊥) +0.062± 0.062 ± 0.005 δ_kCP 0.5(arg Ak− arg Ak) +0.045± 0.069 ± 0.015 δS(Kπ)CP 0.5(arg AKπS − arg A Kπ S ) +0.062± 0.062 ± 0.022 δS(KK)CP 0.5(arg AKKS − arg A KK S ) +0.022± 0.072 ± 0.004

Table 2. Parameters measured in the angular analysis. The first and second uncertainties are statistical and systematic, respectively.

Asymmetry Measured value A1_T(true) _{−0.007 ± 0.012 ± 0.002} A2_T(true) +0.004± 0.014 ± 0.002 A3_T(true) +0.004_{± 0.006 ± 0.001} A4_T(true) +0.002_{± 0.006 ± 0.001} A1 T(fake) −0.105 ± 0.012 ± 0.006 A2_T(fake) _{−0.017 ± 0.014 ± 0.003} A3_T(fake) −0.063 ± 0.006 ± 0.005 A4_T(fake) _{−0.019 ± 0.006 ± 0.007}

Table 3. Triple-product asymmetries. The first and second uncertainties on the measured values are statistical and systematic, respectively.

The numbers of events, N , are determined from fits to the mKKKπ invariant mass

dis-tribution performed separately for B0 _{and B}0 _{decays, identified using the charge of the}

final-state kaon. The dilution from the S-wave components is corrected for using the results of the angular analysis.

The candidates are separated into the TIS and TOS trigger categories. In this study, candidates that are accepted by both trigger decisions are included in both categories and

JHEP05(2014)069

Measurement Acceptance Data/MC Mass model S-wave Total

fL 0.014 0.005 0.002 0.001 0.015 f⊥ 0.013 0.002 0.001 0.001 0.013 fS(Kπ) 0.012 — 0.001 0.002 0.012 fS(KK) 0.007 — 0.002 0.003 0.008 δ⊥ 0.023 0.010 0.006 0.026 0.037 δk 0.029 0.013 0.004 0.024 0.040 δS(Kπ) 0.045 0.026 0.004 0.062 0.081 δS(KK) 0.045 0.005 0.004 0.016 0.048 ACP 0 — 0.002 0.002 0.004 0.005 ACP ⊥ — 0.001 0.006 0.007 0.009 AS(Kπ)CP — 0.007 0.005 0.034 0.035 AS(KK)CP — 0.007 0.009 0.003 0.012 δCP ⊥ — 0.003 0.001 0.004 0.005 δCP_k — 0.005 0.002 0.014 0.015 δS(Kπ)CP — 0.005 0.003 0.021 0.022 δS(KK)CP — 0.002 0.002 0.003 0.004 A1_T(true) — 0.0005 0.0005 0.002 0.002 A2_T(true) — 0.0006 0.0005 0.002 0.002 A3 T(true) — 0.0002 0.0003 0.001 0.001 A4_T(true) — 0.0002 0.0003 0.001 0.001 A1_T(fake) — 0.0019 0.0017 0.005 0.006 A2_T(fake) — 0.0008 0.0008 0.003 0.003 A3_T(fake) — 0.0015 0.0006 0.005 0.005 A4_T(fake) — 0.0003 0.0004 0.007 0.007

Table 4. Systematic uncertainties on the measurement of the polarization amplitudes, relative strong phases and triple-product asymmetries. The column labelled ‘Total’ is the quadratic sum of the individual contributions.

a possible bias to the central value is treated as a systematic uncertainty. The obtained raw asymmetries for the two trigger types are

ATOS_φK∗0 = +0.014± 0.043 and ATIS_φK∗0 =−0.002 ± 0.040 .

The direct CP asymmetry is related to the measured A by

ACP = A− δ with δ= AD+ κdAP, (8.2)

where AD is the detection asymmetry between K+π− and K−π+ final-states, AP is the

asymmetry in production rate between B0 _{and B}0 _{mesons in pp collisions, and the factor}

κd accounts for the dilution of the production asymmetry due to B0− B 0

oscillations. The decay B0 _{→ J/ψK}∗0 _{is used as a control channel to determine the difference in}

asymmetries

JHEP05(2014)069

Parameter LHCb BaBar Belle

fL 0.497± 0.019 ± 0.015 0.494± 0.034 ± 0.013 0.499± 0.030 ± 0.018 f⊥ 0.221± 0.016 ± 0.013 0.212± 0.032 ± 0.013 0.238± 0.026 ± 0.008 δ⊥ 2.633± 0.062 ± 0.037 2.35 ± 0.13 ± 0.09 2.37 ± 0.10 ± 0.04 δk 2.562± 0.069 ± 0.040 2.40 ± 0.13 ± 0.08 2.23 ± 0.10 ± 0.02 ACP 0 −0.003 ± 0.038 ± 0.005 +0.01 ± 0.07 ± 0.02 −0.030 ± 0.061 ± 0.007 ACP ⊥ +0.047± 0.072 ± 0.009 −0.04 ± 0.15 ± 0.06 −0.14 ± 0.11 ± 0.01 δCP_⊥ +0.062_{± 0.062 ± 0.006 +0.21 ± 0.13 ± 0.08} +0.05 _{± 0.10 ± 0.02} δCP_k +0.045± 0.068 ± 0.015 +0.22 ± 0.12 ± 0.08 −0.02 ± 0.10 ± 0.01 Table 5. Comparison of measurements made by the LHCb, BaBar [8] and Belle [11] collaborations. The first uncertainty is statistical and the second systematic.

since the detector and production asymmetries cancel in the difference. Assuming ACP to

be zero for the tree-level B0_{→ J/ψK}∗0 _{decay, ∆A}

CP is the CP asymmetry in B0→ φK∗0.

The sample of B0 _{→ J/ψK}∗0 _{decays, where the J/ψ meson decays to a muon pair, are}

collected through the same trigger and offline selections used for the signal decay mode. Candidates are placed in the TOS trigger category if the trigger decision is based on the decay products from the K∗0_{meson only. Where the decay products from the J/ψ meson}

influences the trigger decision, the candidate is rejected. The raw asymmetries obtained separately for the two trigger types are

ATOS_J/ψK∗0 =−0.003 ± 0.016 and ATIS_J/ψK∗0 =−0.016 ± 0.008 .

After averaging the trigger categories based on their statistical uncertainty, the measured value for the difference in CP asymmetries is

∆ACP = (+1.5± 3.2 ± 0.5) % ,

where the uncertainties are statistical and systematic, respectively. Systematic uncer-tainties arise from the differences between the event topologies of the B0 _{→ J/ψK}∗0 _and

B0→ φK∗0 _{decays. Differences in the behaviour of the events in the TIS trigger category}

between the signal and control modes lead to an uncertainty of 0.25 %. A further uncer-tainty of 0.4 % arises from the differences in kinematics of the daughter particles in the two modes. The double counting of candidates in the overlap region leads to a possible bias on the central value, estimated to be less than 0.1 %.

9 Conclusions

In this paper measurements of the polarization amplitudes and strong phase differences in the decay mode B0_{→ φK}∗0 _{are reported. The results for the P-wave parameters are}

shown in table5; these are consistent with, but more precise than previous measurements. All measurements are consistent with the presence of a large transverse component rather than the na¨ıve expectation of a dominant longitudinal polarization.

JHEP05(2014)069

It is more difficult to make comparisons for the S-wave components as this is the

first measurement to include consistently the effect of the S-wave in the K+_K− _system,

and because the K+_π− _{mass range is different with respect to the range used in previous}

analyses. The measurements of the polarization amplitude differences are consistent with CP conservation.

The results of the angular analysis are used to determine triple-product asymmetries. The measured true asymmetries show no evidence for CP violation. In contrast, large fake asymmetries are observed, indicating the presence of significant final-state interactions. The difference in direct CP asymmetries between the B0 _{→ φK}∗0 _{and B}0 _{→ J/ψK}∗0

decays is also measured,

∆ACP = (+1.5± 3.2 ± 0.5) % ,

where the first uncertainty is statistical and the second systematic. This is a factor of two more precise than previous values reported by BaBar and Belle [8,11] and is found to be consistent with zero.

Acknowledgments

We express our gratitude to our colleagues in the CERN accelerator departments for the excellent performance of the LHC. We thank the technical and administrative staff at the LHCb institutes. We acknowledge support from CERN and from the national agencies: CAPES, CNPq, FAPERJ and FINEP (Brazil); NSFC (China); CNRS/IN2P3 and Region Auvergne (France); BMBF, DFG, HGF and MPG (Germany); SFI (Ireland); INFN (Italy); FOM and NWO (The Netherlands); SCSR (Poland); MEN/IFA (Romania); MinES, Rosatom, RFBR and NRC “Kurchatov Institute” (Russia); MinECo, XuntaGal and GENCAT (Spain); SNSF and SER (Switzerland); NASU (Ukraine); STFC (United Kingdom); NSF (USA). We also acknowledge the support received from EPLANET and the ERC under FP7. The Tier1 computing centres are supported by IN2P3 (France), KIT and BMBF (Germany), INFN (Italy), NWO and SURF (The Netherlands), PIC (Spain), GridPP (United Kingdom). We are indebted to the communities behind the multiple open source software packages on which we depend. We are also thankful for the computing resources and the access to software R&D tools provided by Yandex LLC (Russia).

Open Access. This article is distributed under the terms of the Creative Commons Attribution License (CC-BY 4.0), which permits any use, distribution and reproduction in any medium, provided the original author(s) and source are credited.

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S. Eidelman34_{, S. Eisenhardt}50_{, U. Eitschberger}9_{, R. Ekelhof}9_{, L. Eklund}51,38_{, I. El Rifai}5_,

Ch. Elsasser40_{, S. Esen}11_{, T. Evans}55_{, A. Falabella}16,f_{, C. F¨arber}11_{, C. Farinelli}41_{, S. Farry}52_,

D. Ferguson50_{, V. Fernandez Albor}37_{, F. Ferreira Rodrigues}1_{, M. Ferro-Luzzi}38_{, S. Filippov}33_,

M. Fiore16,f_{, M. Fiorini}16,f_{, M. Firlej}27_{, C. Fitzpatrick}38_{, T. Fiutowski}27_{, M. Fontana}10_,

F. Fontanelli19,j_{, R. Forty}38_{, O. Francisco}2_{, M. Frank}38_{, C. Frei}38_{, M. Frosini}17,38,g_{, J. Fu}21_,

E. Furfaro24,l_{, A. Gallas Torreira}37_{, D. Galli}14,d_{, S. Gambetta}19,j_{, M. Gandelman}2_{, P. Gandini}59_,

Y. Gao3_{, J. Garofoli}59_{, J. Garra Tico}47_{, L. Garrido}36_{, C. Gaspar}38_{, R. Gauld}55_{, L. Gavardi}9_,

E. Gersabeck11_{, M. Gersabeck}54_{, T. Gershon}48_{, Ph. Ghez}4_{, A. Gianelle}22_{, S. Giani’}39_,

V. Gibson47_{, L. Giubega}29_{, V.V. Gligorov}38_{, C. G¨obel}60_{, D. Golubkov}31_{, A. Golutvin}53,31,38_,

A. Gomes1,a_{, H. Gordon}38_{, C. Gotti}20_{, M. Grabalosa G´andara}5_{, R. Graciani Diaz}36_,

L.A. Granado Cardoso38_{, E. Graug´es}36_{, G. Graziani}17_{, A. Grecu}29_{, E. Greening}55_{, S. Gregson}47_,

P. Griffith45_{, L. Grillo}11_{, O. Gr¨unberg}62_{, B. Gui}59_{, E. Gushchin}33_{, Yu. Guz}35,38_{, T. Gys}38_,

C. Hadjivasiliou59_{, G. Haefeli}39_{, C. Haen}38_{, S.C. Haines}47_{, S. Hall}53_{, B. Hamilton}58_,

T. Hampson46_{, X. Han}11_{, S. Hansmann-Menzemer}11_{, N. Harnew}55_{, S.T. Harnew}46_{, J. Harrison}54_,

T. Hartmann62_{, J. He}38_{, T. Head}38_{, V. Heijne}41_{, K. Hennessy}52_{, P. Henrard}5_{, L. Henry}8_,

J.A. Hernando Morata37_{, E. van Herwijnen}38_{, M. Heß}62_{, A. Hicheur}1_{, D. Hill}55_{, M. Hoballah}5_,

C. Hombach54_{, W. Hulsbergen}41_{, P. Hunt}55_{, N. Hussain}55_{, D. Hutchcroft}52_{, D. Hynds}51_,

JHEP05(2014)069

A. Jawahery58_{, M. Jezabek}26_{, F. Jing}3_{, M. John}55_{, D. Johnson}55_{, C.R. Jones}47_{, C. Joram}38_,

B. Jost38_{, N. Jurik}59_{, M. Kaballo}9_{, S. Kandybei}43_{, W. Kanso}6_{, M. Karacson}38_{, T.M. Karbach}38_,

M. Kelsey59_{, I.R. Kenyon}45_{, T. Ketel}42_{, B. Khanji}20_{, C. Khurewathanakul}39_{, S. Klaver}54_,

O. Kochebina7_{, M. Kolpin}11_{, I. Komarov}39_{, R.F. Koopman}42_{, P. Koppenburg}41,38_{, M. Korolev}32_,

A. Kozlinskiy41_{, L. Kravchuk}33_{, K. Kreplin}11_{, M. Kreps}48_{, G. Krocker}11_{, P. Krokovny}34_,

F. Kruse9_{, M. Kucharczyk}20,26,38,k_{, V. Kudryavtsev}34_{, K. Kurek}28_{, T. Kvaratskheliya}31_,

V.N. La Thi39_{, D. Lacarrere}38_{, G. Lafferty}54_{, A. Lai}15_{, D. Lambert}50_{, R.W. Lambert}42_,

E. Lanciotti38_{, G. Lanfranchi}18_{, C. Langenbruch}38_{, B. Langhans}38_{, T. Latham}48_{, C. Lazzeroni}45_,

R. Le Gac6_{, J. van Leerdam}41_{, J.-P. Lees}4_{, R. Lef`evre}5_{, A. Leflat}32_{, J. Lefran¸cois}7_{, S. Leo}23_,

O. Leroy6_{, T. Lesiak}26_{, B. Leverington}11_{, Y. Li}3_{, M. Liles}52_{, R. Lindner}38_{, C. Linn}38_,

F. Lionetto40_{, B. Liu}15_{, G. Liu}38_{, S. Lohn}38_{, I. Longstaff}51_{, I. Longstaff}51_{, J.H. Lopes}2_,

N. Lopez-March39_{, P. Lowdon}40_{, H. Lu}3_{, D. Lucchesi}22,q_{, H. Luo}50_{, A. Lupato}22_{, E. Luppi}16,f_,

O. Lupton55_{, F. Machefert}7_{, I.V. Machikhiliyan}31_{, F. Maciuc}29_{, O. Maev}30_{, S. Malde}55_,

G. Manca15,e_{, G. Mancinelli}6_{, M. Manzali}16,f_{, J. Maratas}5_{, J.F. Marchand}4_{, U. Marconi}14_,

C. Marin Benito36_{, P. Marino}23,s_{, R. M¨arki}39_{, J. Marks}11_{, G. Martellotti}25_{, A. Martens}8_,

A. Mart´ın S´anchez7_{, M. Martinelli}41_{, D. Martinez Santos}42_{, F. Martinez Vidal}64_,

D. Martins Tostes2_{, A. Massafferri}1_{, R. Matev}38_{, Z. Mathe}38_{, C. Matteuzzi}20_{, A. Mazurov}16,38,f_,

M. McCann53_{, J. McCarthy}45_{, A. McNab}54_{, R. McNulty}12_{, B. McSkelly}52_{, B. Meadows}57,55_,

F. Meier9_{, M. Meissner}11_{, M. Merk}41_{, D.A. Milanes}8_{, M.-N. Minard}4_{, J. Molina Rodriguez}60_,

S. Monteil5_{, D. Moran}54_{, M. Morandin}22_{, P. Morawski}26_{, A. Mord`a}6_{, M.J. Morello}23,s_,

J. Moron27_{, R. Mountain}59_{, F. Muheim}50_{, K. M¨uller}40_{, R. Muresan}29_{, B. Muster}39_{, P. Naik}46_,

T. Nakada39_{, R. Nandakumar}49_{, I. Nasteva}1_{, M. Needham}50_{, N. Neri}21_{, S. Neubert}38_,

N. Neufeld38_{, M. Neuner}11_{, A.D. Nguyen}39_{, T.D. Nguyen}39_{, C. Nguyen-Mau}39,p_{, M. Nicol}7_,

V. Niess5_{, R. Niet}9_{, N. Nikitin}32_{, T. Nikodem}11_{, A. Novoselov}35_{, A. Oblakowska-Mucha}27_,

V. Obraztsov35_{, S. Oggero}41_{, S. Ogilvy}51_{, O. Okhrimenko}44_{, R. Oldeman}15,e_{, G. Onderwater}65_,

M. Orlandea29_{, J.M. Otalora Goicochea}2_{, P. Owen}53_{, A. Oyanguren}64_{, B.K. Pal}59_{, A. Palano}13,c_,

F. Palombo21,t_{, M. Palutan}18_{, J. Panman}38_{, A. Papanestis}49,38_{, M. Pappagallo}51_{, C. Parkes}54_,

C.J. Parkinson9_{, G. Passaleva}17_{, G.D. Patel}52_{, M. Patel}53_{, C. Patrignani}19,j_{, A. Pazos Alvarez}37_,

A. Pearce54_{, A. Pellegrino}41_{, M. Pepe Altarelli}38_{, S. Perazzini}14,d_{, E. Perez Trigo}37_{, P. Perret}5_,

M. Perrin-Terrin6_{, L. Pescatore}45_{, E. Pesen}66_{, K. Petridis}53_{, A. Petrolini}19,j_,

E. Picatoste Olloqui36_{, B. Pietrzyk}4_{, T. Pilaˇr}48_{, D. Pinci}25_{, A. Pistone}19_{, S. Playfer}50_,

M. Plo Casasus37_{, F. Polci}8_{, A. Poluektov}48,34_{, E. Polycarpo}2_{, A. Popov}35_{, D. Popov}10_,

B. Popovici29_{, C. Potterat}2_{, A. Powell}55_{, J. Prisciandaro}39_{, A. Pritchard}52_{, C. Prouve}46_,

V. Pugatch44_{, A. Puig Navarro}39_{, G. Punzi}23,r_{, W. Qian}4_{, B. Rachwal}26_{, J.H. Rademacker}46_,

B. Rakotomiaramanana39_{, M. Rama}18_{, M.S. Rangel}2_{, I. Raniuk}43_{, N. Rauschmayr}38_{, G. Raven}42_,

S. Reichert54_{, M.M. Reid}48_{, A.C. dos Reis}1_{, S. Ricciardi}49_{, A. Richards}53_{, K. Rinnert}52_,

V. Rives Molina36_{, D.A. Roa Romero}5_{, P. Robbe}7_{, A.B. Rodrigues}1_{, E. Rodrigues}54_,

P. Rodriguez Perez54_{, S. Roiser}38_{, V. Romanovsky}35_{, A. Romero Vidal}37_{, M. Rotondo}22_,

J. Rouvinet39_{, T. Ruf}38_{, F. Ruffini}23_{, H. Ruiz}36_{, P. Ruiz Valls}64_{, G. Sabatino}25,l_,

J.J. Saborido Silva37_{, N. Sagidova}30_{, P. Sail}51_{, B. Saitta}15,e_{, V. Salustino Guimaraes}2_,

C. Sanchez Mayordomo64_{, B. Sanmartin Sedes}37_{, R. Santacesaria}25_{, C. Santamarina Rios}37_,

E. Santovetti24,l_{, M. Sapunov}6_{, A. Sarti}18,m_{, C. Satriano}25,n_{, A. Satta}24_{, M. Savrie}16,f_,

D. Savrina31,32_{, M. Schiller}42_{, H. Schindler}38_{, M. Schlupp}9_{, M. Schmelling}10_{, B. Schmidt}38_,

O. Schneider39_{, A. Schopper}38_{, M.-H. Schune}7_{, R. Schwemmer}38_{, B. Sciascia}18_{, A. Sciubba}25_,

M. Seco37_{, A. Semennikov}31_{, K. Senderowska}27_{, I. Sepp}53_{, N. Serra}40_{, J. Serrano}6_{, L. Sestini}22_,

P. Seyfert11_{, M. Shapkin}35_{, I. Shapoval}16,43,f_{, Y. Shcheglov}30_{, T. Shears}52_{, L. Shekhtman}34_,

V. Shevchenko63_{, A. Shires}9_{, R. Silva Coutinho}48_{, G. Simi}22_{, M. Sirendi}47_{, N. Skidmore}46_,

JHEP05(2014)069

M.D. Sokoloff57_{, F.J.P. Soler}51_{, F. Soomro}39_{, D. Souza}46_{, B. Souza De Paula}2_{, B. Spaan}9_,

A. Sparkes50_{, F. Spinella}23_{, P. Spradlin}51_{, F. Stagni}38_{, S. Stahl}11_{, O. Steinkamp}40_,

O. Stenyakin35_{, S. Stevenson}55_{, S. Stoica}29_{, S. Stone}59_{, B. Storaci}40_{, S. Stracka}23,38_,

M. Straticiuc29_{, U. Straumann}40_{, R. Stroili}22_{, V.K. Subbiah}38_{, L. Sun}57_{, W. Sutcliffe}53_,

K. Swientek27_{, S. Swientek}9_{, V. Syropoulos}42_{, M. Szczekowski}28_{, P. Szczypka}39,38_{, D. Szilard}2_,

T. Szumlak27_{, S. T’Jampens}4_{, M. Teklishyn}7_{, G. Tellarini}16,f_{, E. Teodorescu}29_{, F. Teubert}38_,

C. Thomas55_{, E. Thomas}38_{, J. van Tilburg}41_{, V. Tisserand}4_{, M. Tobin}39_{, S. Tolk}42_,

L. Tomassetti16,f_{, D. Tonelli}38_{, S. Topp-Joergensen}55_{, N. Torr}55_{, E. Tournefier}4_{, S. Tourneur}39_,

M.T. Tran39_{, M. Tresch}40_{, A. Tsaregorodtsev}6_{, P. Tsopelas}41_{, N. Tuning}41_{, M. Ubeda Garcia}38_,

A. Ukleja28_{, A. Ustyuzhanin}63_{, U. Uwer}11_{, V. Vagnoni}14_{, G. Valenti}14_{, A. Vallier}7_,

R. Vazquez Gomez18_{, P. Vazquez Regueiro}37_{, C. V´azquez Sierra}37_{, S. Vecchi}16_{, J.J. Velthuis}46_,

M. Veltri17,h_{, G. Veneziano}39_{, M. Vesterinen}11_{, B. Viaud}7_{, D. Vieira}2_{, M. Vieites Diaz}37_,

X. Vilasis-Cardona36,o_{, A. Vollhardt}40_{, D. Volyanskyy}10_{, D. Voong}46_{, A. Vorobyev}30_,

V. Vorobyev34_{, C. Voß}62_{, H. Voss}10_{, J.A. de Vries}41_{, R. Waldi}62_{, C. Wallace}48_{, R. Wallace}12_,

J. Walsh23_{, S. Wandernoth}11_{, J. Wang}59_{, D.R. Ward}47_{, N.K. Watson}45_{, A.D. Webber}54_,

D. Websdale53_{, M. Whitehead}48_{, J. Wicht}38_{, D. Wiedner}11_{, G. Wilkinson}55_{, M.P. Williams}45_,

M. Williams56_{, F.F. Wilson}49_{, J. Wimberley}58_{, J. Wishahi}9_{, W. Wislicki}28_{, M. Witek}26_,

G. Wormser7_{, S.A. Wotton}47_{, S. Wright}47_{, S. Wu}3_{, K. Wyllie}38_{, Y. Xie}61_{, Z. Xing}59_{, Z. Xu}39_,

Z. Yang3_{, X. Yuan}3_{, O. Yushchenko}35_{, M. Zangoli}14_{, M. Zavertyaev}10,b_{, F. Zhang}3_{, L. Zhang}59_,

W.C. Zhang12_{, Y. Zhang}3_{, A. Zhelezov}11_{, A. Zhokhov}31_{, L. Zhong}3_{, A. Zvyagin}38

1

Centro Brasileiro de Pesquisas F´ısicas (CBPF), Rio de Janeiro, Brazil 2 _{Universidade Federal do Rio de Janeiro (UFRJ), Rio de Janeiro, Brazil} 3 _{Center for High Energy Physics, Tsinghua University, Beijing, China} 4 _{LAPP, Universit´e de Savoie, CNRS/IN2P3, Annecy-Le-Vieux, France}

5 _{Clermont Universit´e, Universit´e Blaise Pascal, CNRS/IN2P3, LPC, Clermont-Ferrand, France} 6 _{CPPM, Aix-Marseille Universit´e, CNRS/IN2P3, Marseille, France}

7

LAL, Universit´e Paris-Sud, CNRS/IN2P3, Orsay, France 8

LPNHE, Universit´e Pierre et Marie Curie, Universit´e Paris Diderot, CNRS/IN2P3, Paris, France 9

Fakult¨at Physik, Technische Universit¨at Dortmund, Dortmund, Germany 10

Max-Planck-Institut f¨ur Kernphysik (MPIK), Heidelberg, Germany 11

Physikalisches Institut, Ruprecht-Karls-Universit¨at Heidelberg, Heidelberg, Germany 12

School of Physics, University College Dublin, Dublin, Ireland 13

Sezione INFN di Bari, Bari, Italy 14 _{Sezione INFN di Bologna, Bologna, Italy} 15 _{Sezione INFN di Cagliari, Cagliari, Italy} 16 _{Sezione INFN di Ferrara, Ferrara, Italy} 17 _{Sezione INFN di Firenze, Firenze, Italy}

18 _{Laboratori Nazionali dell’INFN di Frascati, Frascati, Italy} 19

Sezione INFN di Genova, Genova, Italy 20

Sezione INFN di Milano Bicocca, Milano, Italy 21

Sezione INFN di Milano, Milano, Italy 22

Sezione INFN di Padova, Padova, Italy 23

Sezione INFN di Pisa, Pisa, Italy 24

Sezione INFN di Roma Tor Vergata, Roma, Italy 25

Sezione INFN di Roma La Sapienza, Roma, Italy

26 _{Henryk Niewodniczanski Institute of Nuclear Physics Polish Academy of Sciences, Krak´ow, Poland} 27 _{AGH - University of Science and Technology, Faculty of Physics and Applied Computer Science,}

Krak´ow, Poland

JHEP05(2014)069

29 _{Horia Hulubei National Institute of Physics and Nuclear Engineering, Bucharest-Magurele,} Romania

30

Petersburg Nuclear Physics Institute (PNPI), Gatchina, Russia 31

Institute of Theoretical and Experimental Physics (ITEP), Moscow, Russia 32

Institute of Nuclear Physics, Moscow State University (SINP MSU), Moscow, Russia 33

Institute for Nuclear Research of the Russian Academy of Sciences (INR RAN), Moscow, Russia 34

Budker Institute of Nuclear Physics (SB RAS) and Novosibirsk State University, Novosibirsk, Russia

35

Institute for High Energy Physics (IHEP), Protvino, Russia 36 _{Universitat de Barcelona, Barcelona, Spain}

37 _{Universidad de Santiago de Compostela, Santiago de Compostela, Spain} 38 _{European Organization for Nuclear Research (CERN), Geneva, Switzerland} 39 _{Ecole Polytechnique F´ed´erale de Lausanne (EPFL), Lausanne, Switzerland} 40 _{Physik-Institut, Universit¨at Z¨urich, Z¨urich, Switzerland}

41

Nikhef National Institute for Subatomic Physics, Amsterdam, The Netherlands 42

Nikhef National Institute for Subatomic Physics and VU University Amsterdam, Amsterdam, The Netherlands

43

NSC Kharkiv Institute of Physics and Technology (NSC KIPT), Kharkiv, Ukraine 44

Institute for Nuclear Research of the National Academy of Sciences (KINR), Kyiv, Ukraine 45

University of Birmingham, Birmingham, United Kingdom 46

H.H. Wills Physics Laboratory, University of Bristol, Bristol, United Kingdom 47 _{Cavendish Laboratory, University of Cambridge, Cambridge, United Kingdom} 48 _{Department of Physics, University of Warwick, Coventry, United Kingdom} 49 _{STFC Rutherford Appleton Laboratory, Didcot, United Kingdom}

50 _{School of Physics and Astronomy, University of Edinburgh, Edinburgh, United Kingdom} 51 _{School of Physics and Astronomy, University of Glasgow, Glasgow, United Kingdom} 52

Oliver Lodge Laboratory, University of Liverpool, Liverpool, United Kingdom 53

Imperial College London, London, United Kingdom 54

School of Physics and Astronomy, University of Manchester, Manchester, United Kingdom 55

Department of Physics, University of Oxford, Oxford, United Kingdom 56

Massachusetts Institute of Technology, Cambridge, MA, United States 57

University of Cincinnati, Cincinnati, OH, United States 58

University of Maryland, College Park, MD, United States 59 _{Syracuse University, Syracuse, NY, United States}

60 _{Pontif´ıcia Universidade Cat´olica do Rio de Janeiro (PUC-Rio), Rio de Janeiro, Brazil,} associated to2

61 _{Institute of Particle Physics, Central China Normal University, Wuhan, Hubei, China,} associated to3

62

Institut f¨ur Physik, Universit¨at Rostock, Rostock, Germany, associated to11 63

National Research Centre Kurchatov Institute, Moscow, Russia, associated to31 64

Instituto de Fisica Corpuscular (IFIC), Universitat de Valencia-CSIC, Valencia, Spain, associated to36

65

KVI - University of Groningen, Groningen, The Netherlands, associated to41 66

Celal Bayar University, Manisa, Turkey, associated to38 a

Universidade Federal do Triˆangulo Mineiro (UFTM), Uberaba-MG, Brazil

b _{P.N. Lebedev Physical Institute, Russian Academy of Science (LPI RAS), Moscow, Russia} c _{Universit`a di Bari, Bari, Italy}

d _{Universit`a di Bologna, Bologna, Italy</sub> e <sub>Universit`a di Cagliari, Cagliari, Italy} f

Universit`a di Ferrara, Ferrara, Italy g