[Solid_ec] Problem solved in Ye (Syracuse)'s LHCb TDR plot

[tianye at jlab.org]

Hi Xiaochao,

Thanks a lot for your explanation and suggestion.

My previous result shows that the 2X0 prelead configuration degrades SOLID
ECAL energy resolution from 4% to 6.2%,  and I try to use the Fig.3.5 to
show that my result is consistent with the LHCb simulation study, which
shows that 2X0 prelead degrades their ideal energy resolution from 2.5% to
4%.

I will study the lead thickness and the angle influence next. Thanks.

Best,
Ye


> Hi Ye (Syracuse) et al.:
>
> Reading LHCb TDR again I think I understand what's going on:
>
> LHCb TDR can be found at
> http://lhcb-calo.web.cern.ch/lhcb-calo/html/TDR/calo_tdr.pdf
>
> The relevant figures are 3.3, 3.4, and 3.5.  In Fig.3.3, they showed the
> effect of the fluctuation in the energy deposit in the lead layer. It adds
> to the energy resolution of the ECal. For 2Xo, if I assume the first point
> is for 1 GeV electrons, it shows additional 4% fluctuation. Which for LHCb
> is okay but for us may be too large.
>
> For Fig.3.5 which is what triggered the problem in our meeting: if you
> read the TDR carefully, this figure is to show the lead converter effect
> (with and without correction using preshower signal) to an ideal ECal,
> where the ideal ECal is with pre-defined resolution of 2.5%/sqrt(E). They
> added this ideal ECal behind the Preshower in the simulation and study how
> the performance change with and without prelead and preshower and their
> corrections.
>
> Hence, the 2.5%/sqrt(E) is NOT LHCb performance nor their designed
> specification. It's an artificial number input to the simulation.
>
> To move forward, I suggest Ye look into:
>
> 1) scanning lead thickness from 0.5 to 2.0 X0, and study the resulting
> energy resolution; Paul is right that at an angle the actual lead
> thickness is larger than 2X0 for our setup right now and this will add
> additional fluctuation to the energy resolution.
>
> 2) when calculating energy resolution, consider correcting for the energy
> loss in the pre-lead using the preshower readout, as LHCb did in Fig.3.4
>
> Xiaochao
>
> ----- Original Message -----
>> From: "Xiaochao Zheng" <xiaochao at jlab.org>
>> To: "solid ec" <solid_ec at jlab.org>, "Solid daq" <solid_daq at jlab.org>
>> Sent: Wednesday, June 14, 2017 10:27:34 PM
>> Subject: SoLID EC/DAQ meeting 9:30am Thursday 6/15/2017 CC F227
>
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>> Xiaochao
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