Azimuthal symmetry of HCAL readouts. O. Kodolova (SINP MSU). f symmetry: goal and data stream choice. Goal is to install the relative scale within each eta-ring. - using the phi-symmetric events equalize the response of HCAL readouts
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O. Kodolova (SINP MSU)
Goal is to install the relative scale within each eta-ring.
- using the phi-symmetric events equalize the response of HCAL
- choice of data stream may be different for the different eta
Current data stream choices:
- minbias events
- low momentum isolated tracks (10-15-25 GeV)
Both choices have + and - features
The estimation of mean energy per readout:
<Ereadout> = <Esignal>+<Enoise>
The variance estimation:
<Vreadout> = <Vsignal>+<Vnoise>
The mean energy and variance in the ring:
<Ering> = <Esignal>+<Enoise>
Noise mean values and variances have to be estimated either from the same event using first time slices (startup scenario) or from pedestal runs (when pileup starts).
Coefficients are derived from non-calibrated sample for each
readout i in each -ring j after Noise subtraction
Cij = <Eij>/<Ej>
Cij = sqrt(<Vij>/<Vj>)
Coefficients are applied and the new readout response is:
Note: to avoid noise/signal
correlations special runs
Eij corrected = Eij/Cij
Project was started in 2006 and was tested
10 mln (noise+signal)
Signal is much
less then noise
2 mln (noise)
needed statistics estimation
Depends on the noise value, i.e. Most critical for the central barrel
1. Calibration with mean value: Mean noise = 10-5 with RMS=0.2-0.3 GeV
HB: 0.002 GeV (ieta=1)
HB: 0.008 GeV (ieta=14)
HE: 0.03 GeV (ieta=21)
HF: 0.5 GeV (ieta=35)
2. Calibration with variance: Mean Noise variance =0.084, RMS=0.24 GeV2
HB: 0.005 GeV2 (ieta=1)
HB: 0.008 GeV2 (ieta=14)
HE: 0.059 GeV2 (ieta=21)
Error of noise RMS/sqrt(N)
< 0.02 * Esignal
N=25 mlns events for HB, ieta=1
Error of noise RMS/sqrt(N)
< 0.02 * Vsignal
N=6 mlns events for HB, ieta=1
for 9 mlns events
Channels with large noise RMS
require higher statistics
(optimistic) or can not be included
in f-symmetry if noise distribution
is essentially non-gausian
Large noise channels
were extracted from the
The best accuracy
that can be achieved
with 9 mlns of events
and current noise map
L1 trigger : EG and Muon
AlCaRAW is created at HLT step to be sent to Tier0
only HCAL RAW data (without zero-suppression)
Special reconstruction at Tier0 followed by
Time slices 1-4 for noise reconstruction
Time slices 5-8 for signal reconstruction
160 mlns events are at CAF: same amount for noise and signal events.
50 mlns were analyzed:
4 days of data collected from 29st of Oct to 1st of Nov.
~2 days with HF on.
It can be used to study
the level of noise and
Energy distribution in the readout
twice wider then “normal” readouts
due to small conversion factor.
Problematic HPD, iphi=70
From 29th Oct to 1st of Nov
HF was on later (on 30th Oct?)
HB, iph=70. ieta=-1
HF, ieta=36, iphi=3
Variances are stable, but
sometimes we observe fluctuations
that required the additional study.
cell-by-cell calibration with isotracks
- statistics for tracks with P>15 GeV/c
we need a few hundreds MIP tracks per cell
- material effects which depend on track energy
- shower profile vs energy ?
We will use the interval from 15 to 25 GeV or from
10 to 25 GeV
- Zero suppression affects low momentum tracks ?
Phi symmetry in high -h region (outside tracker) can be done with
minbias events with accuracy less than 1 %. For HB we can reach
3-3.5% in rings ieta<5 and 2% in ieta=5-14 and in HE. ~10 mlns events
have to be collected in special NZSP run.
The possibility was checked with CSA07/CSA08/Latest generation with
Phi symmetry in HB/HE can be done/cross-checked with isolated tracks
sample. However this possibility needs some additional study.
More study need to be done with Cosmic (noise stability) and with new
simulation with the latest noise/gains.