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CMS-DP-2017/003

ECAL Laser monitoring till end of 2016 and ECAL phi-symmetry

Abstract: ECAL Laser monitoring till end of 2016 and ECAL phi-symmetry.

CDS entry

iCMS entry


Figure Caption
pdf version
histories 2011-2012-2015-2016 161212.png
Relative response to laser light (440 nm in 2011 and 447 nm from
2012 onwards) injected in the ECAL crystals, measured by the ECAL
laser monitoring system, averaged over all crystals in bins of
pseudorapidity, for the 2011, 2012, 2015 and 2016 data taking periods,
with magnetic field at 3.8 T. The response change observed in the
ECAL channels is up to 10% in the barrel and it reaches up to 50% at η
~ 2.5, the limit of the tracker acceptance. The response change is up to
90% in the region closest to the beam pipe. The recovery of the crystal
response during the Long-Shutdown-1 period is visible, where the
response was not fully recovered, particularly in the region closest to
the beam pipe. These measurements are used to correct the physics
data. This is an update of the plots appearing in CMS-DP-2012/007,
CMS-DP-2012/015, CMS-DP-2015/016, CMS-DP-2015/063,
and CMS-DP-2016/031 and includes measurements taken up to
November 2016. The bottom plot shows the instantaneous LHC
luminosity delivered during this time period.
pdf version
history point.png

Distribution of the ratio of the intercalibration coefficients (IC) for all the channels in
the CMS ECAL barrel (η < 1.5). The IC are derived exploiting the azimuthal
symmetry of zero bias events: each IC set is derived with more than 80 million events
collected over no more than two days which gives a statistical precision of about 0.4%
on the IC ratio.
The blue histogram is the ratio (IC Sep /IC May ) between the last time period used for the
monitoring during 2016 and the first one, while the red histogram (IC Sep (8th) /IC Sep (7th) ) is
the ratio between the values derived in the last period (8 th of September) and the one
derived in the period immediately before (7 th of September).
The first and last periods are separated by four months while the typical time period
between two successive calibration points is less than 48 hours.
The plot shows that the channel intercalibration coefficients vary significantly over a
period of several months.
For a review of the f-symmetry method see: “Energy calibration and resolution of the
CMS electromagnetic calorimeter in pp collisions at √s = 7 TeV”, J. Instrum. 8 (2013)
P09009
pdf version
history EB.png

The plots show the relative variation of the intercalibration coefficients (IC) of the CMS ECAL
during 2016 data taking. The IC are derived such that for channels located at the same
pseudorapidity η the average is one, while the intercalibration of different η regions is then set
using Z → e + e - events.
The monitoring is performed exploiting the azimuthal symmetry of zero bias events: each IC
set is derived with more than 80 million events collected over no more that two days, which
provide a statistical precision of about 0.4% on the ratio of IC. The left plot includes channels
in the barrel (η < 1.5) while the right one in the endcaps (η > 1.5).
For each channel and for each point in time two ratios are computed: IC n /IC n-1 and IC n /IC 0 being
n, n-1 and 0 the current, previous and first point of the year.
The standard deviation of the two ratios is computed at each time period and is plotted versus
time: blue points (IC n /IC 0 , relative to the start of 2016); red points (IC n /IC n-1 , relative to the
previous calibration point).
The width of the ratio of IC relative to the start of 2016 increases with time, whereas it remains
constant for close time periods.
For a review of the f-symmetry method see: “Energy calibration and resolution of the CMS
electromagnetic calorimeter in pp collisions at √s = 7 TeV”, J. Instrum. 8 (2013) P09009
pdf version
history EE.png

The plots show the relative variation of the intercalibration coefficients (IC) of the CMS ECAL
during 2016 data taking. The IC are derived such that for channels located at the same
pseudorapidity η the average is one, while the intercalibration of different η regions is then set
using Z → e + e - events.
The monitoring is performed exploiting the azimuthal symmetry of zero bias events: each IC
set is derived with more than 80 million events collected over no more that two days, which
provide a statistical precision of about 0.4% on the ratio of IC. The left plot includes channels
in the barrel (η < 1.5) while the right one in the endcaps (η > 1.5).
For each channel and for each point in time two ratios are computed: IC n /IC n-1 and IC n /IC 0 being
n, n-1 and 0 the current, previous and first point of the year.
The standard deviation of the two ratios is computed at each time period and is plotted versus
time: blue points (IC n /IC 0 , relative to the start of 2016); red points (IC n /IC n-1 , relative to the
previous calibration point).
The width of the ratio of IC relative to the start of 2016 increases with time, whereas it remains
constant for close time periods.
For a review of the f-symmetry method see: “Energy calibration and resolution of the CMS
electromagnetic calorimeter in pp collisions at √s = 7 TeV”, J. Instrum. 8 (2013) P09009

-- AndreaMassironi - 2017-02-17

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PDFpdf histories_2011-2012-2015-2016_161212.pdf r1 manage 4511.1 K 2017-02-17 - 16:12 AndreaMassironi  
PNGpng histories_2011-2012-2015-2016_161212.png r1 manage 121.8 K 2017-02-17 - 16:12 AndreaMassironi  
PDFpdf history_EB.pdf r1 manage 16.8 K 2017-02-17 - 16:12 AndreaMassironi  
PNGpng history_EB.png r1 manage 26.6 K 2017-02-17 - 16:12 AndreaMassironi  
PDFpdf history_EE.pdf r1 manage 16.7 K 2017-02-17 - 16:12 AndreaMassironi  
PNGpng history_EE.png r1 manage 26.8 K 2017-02-17 - 16:12 AndreaMassironi  
PDFpdf history_point.pdf r1 manage 15.3 K 2017-02-17 - 16:12 AndreaMassironi  
PNGpng history_point.png r1 manage 20.4 K 2017-02-17 - 16:12 AndreaMassironi  
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