SiPM for MEG2

SiPM for MEG2

On behalf of the italianTC group

Fukuoka 23 Oct 2013

Current TC time resolution

Intrinsic TC resolution at BTF is ~40 ps In MEG degradation due to B and to large dynamic range

40 ps → 50 ps expected

Additional degradation due

to DRS ( σ DrS(t) ~30-50ps) → 60 ps ( measured with triple, 65 ps is an

overestimation )

Current t _{e γ} resolution

Dominant contribution from t

σ( TC+DRS) =

σ( BTF)(1+ σ( MEG))+

σ( DRS) =

40x(1 + 0.25) + 40 = 60 ps

σ( BTF) intrinsec ( from BTF ) σ( MEG) relative degradation due to B (low G), large

signal dynamic range

σ( DRS) due to DRS

Upgrade TC time resolution

Resolution σ (t

) = 30 (33) ps measured

MEG Additional error (B, extra dynamic range): 1.1 Reduced DRS error: 25 ps

Calibration: 30 ps(???)

Upgrade t _{e γ} resolution

MEG MEG2(my) MEG2(proposal)

Intrinsec 40 ps → 30 ps 35 ps MEG factor 0.25 0.1

DRS 40 ps 25 ps TC calib 40 ps 30 ps

Le/c 75 ps 35 ps 11 ps ---

t

107 ps 63 ps 37 ps

t

67 ps → 64 ps 76 ps

---

t

122 ps 90 ps ^{84 ps}

t _{e γ} in alternative scenarios

• t

intrinsic = 20 ps -> t

= 87 ps

• t

intrinsic = 30 ps -> t

= 90 ps (Hamamatsu)

• t

intrinsic = 33 ps -> t

= 91 ps (AdvanSId)

• t

intrinsic = 40 ps -> t

= 93 ps

• σ (calibration) = 30ps

• The change are tiny.

• Limit on µ ->e γ scales linearly with resolution

• But 1 more week/y per extra calibration or

commissioning would waste a 3% gain

Calibration and σ( t _{e γ} )

Relative calibration between TC counter

(and with XEC) can strongly influence σ (t

) 

Stability of the SiPM is of paramount importance

In particular the thermal coefficients dV/dT should be as small as possible

That is the discriminating parameters for devices with comparable σ (t

)

dV/dT = 50 mV/

C for (Hamamatsu)

dV/dT = 25 mV/

C for (AdvanSid)

Conclusion

Hamamatsu and AdvanSid are equivalent from the point of view of the effect on t

time resolution

AdvanSid offers better performance from the point of view of stability needed for precise cailbration

AdvanSid is our preferred choice for MEG2