Transcript Status of the CMS Detector The LHC and Dark Matter Ann Arbor, Michigan, January 6th -9th, 2009 Paolo Rumerio, University of Maryland On Behalf.

Status of the CMS Detector
The LHC and Dark Matter
Ann Arbor, Michigan, January 6th -9th, 2009
Paolo Rumerio, University of Maryland
On Behalf of the CMS Collaboration
Overview
 Installation and Commissioning
 Beam Days
 Cosmic Run at Four Tesla
 Winter Shutdown Activities
LHCDM, Ann Arbor, Jan 6th - 9th, 2009
Paolo Rumerio, Maryland
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The CMS Detector
3.8T solenoid
YB0
HCAL
YE-1
Muon
chambers
Pixel
Si Tracker
ECAL
Iron yoke
Some detector component acronyms:
Pixel: Barrel (BPix) and Endcap disks (FPix)
Tracker: Inner Barrel (TIB), Inner Disks (TID), Outer Barrel (TOB), Endcaps (TEC)
Electromagnetic Calorimeter: ECAL Barrel (EB) and ECAL Endcaps (EE)
Hadronic Calorimeter: HCAL Barrel (HB), HCAL Endcap (HE), HCAL Forward (HF), HCAL Outer (HO)
Muon Chambers: Drift Tubes (DT) in the barrel (also Muon Barrel - MB), Cathode Strip Chambers (CSC) in the endcaps
(also Muon Endcaps - ME), Resistive Plate Chambers (RPC) in barrel end endcaps
Magnetic field return yoke: Yoke Barrel (YB) and Yoke Endcaps (YE)
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Lowering Barrel Wheels and Endcap Disks
Endcap disks:
Jan. 07 – Jan. 08
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Barrel wheels:
Jan. - Oct. 2007
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Installing Detectors Inside the Magnet
Inserting HCAL barrel:
Mar. 07
Installing ECAL Barrel:
ended July 07
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YB0 After Cabling
Dec. 07
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Inserting Silicon Strip Tracker: Dec 08.
Cabling completed Mar. 08
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Latest Installed Components
ECAL endcaps:
completed and
fully installed
Aug. 08
Beam pipe:
insertion and
bakeout
June 08
Pixels: inserted
Aug. 08
LHCDM, Ann Arbor, Jan 6th - 9th, 2009
 EE and Pixels were installed just before
beam and worked quite well very soon
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CMS Closed – 3 September 2008
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Commissioning
 Magnet Test and Cosmic Challenge (MTCC) took place in summer 2006 on the
surface of the experiment location
 Commissioning of the magnet and measuring of the field map
 Test of a vertical slice of the detector and cosmic data taking
 Since May 2007, three- to ten-day-long exercises took place underground with
the installed detector components, electronics and services
 Increasing size and number of participants, and scope of the exercises
 Balancing with
Detector Participation
installation schedule
versus Time
and detector local
commissioning
LHCDM, Ann Arbor, Jan 6th - 9th, 2009
Paolo Rumerio, Maryland
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Cosmic Runs Without Magnetic Field
 Since March 2008,
global runs saw an
increasing focus on
 stability of operations
 cosmic ray data
taking (hence named
CRUZET - Cosmic
RUns at ZEro Tesla)
Events Collected
Versus Time
CRUZET4 : Pixel tracker and EE
join (final CMS configuration)
CRUZET3:
Strip tracker joins
Sept.10:
Beam
CRUZET2
CRUZET1
End March 08
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First Beam
 Sun and Mon, Sept. 7 and 8
 Beam 1 (clockwise) single
“shots” onto a collimator 150
meters upstream of CMS
(also called “splash” events)
 Tue, Sept. 9
 20 additional shots as above
 Wed, Sept. 10
 Circulating beams, beam 1
in the morning, beam 2 in
Beam Pickup and
CMS Beam Condition Monitors
the afternoon
 Thu, Sept. 11
 RF capture of beam
 Fri, Sept. 19th
 A faulty electrical connection between a dipole and a quadrupole failed,
massive helium loss, and cryogenics and vacuum lost
 Beam elements in the region are being extracted and replaced or repaired
During all of these activities, CMS triggered and recorded data
(without CMS magnetic field and with inner tracking systems kept off)
LHCDM, Ann Arbor, Jan 6th - 9th, 2009
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Event Display
of a Beam-on-Collimator Event
HCAL Energy
ECAL Energy
From
2x10^9
protons
on a
collimator
150 m
upstream
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Drift Tube hits
11
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ECAL vs. HCAL Energy Correlation
in Beam-on-Collimator Events
 Correlation between reconstructed energy in the CMS Hadron Barrel calorimeter (HB)
and Electron Barrel Calorimeter (EB) for beam-on-collimator events in September 2008.
 The large reconstructed energy values are the result of the hundreds of thousands
of muons which passed through the detector during each event.
LHCDM, Ann Arbor, Jan 6th - 9th, 2009
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Muon Chamber Number of Hits
in Beam-on-Collimator Events
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 Linearity of the number of hits in the third ring of DT chambers vs.
total ECAL energy for beam-on-collimator events
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Synchronization of HCAL
from Beam-on-Collimator Events
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The pulse arrival time of beam-on-collimator events is predicted using
geometry considerations
Left panel: difference between predicted and mean pulse arrival time
 beam-on-collimator events of Sep. 10.
 HCAL barrel uses tuned integration delays, while HCAL endcap,
forward and outer use not tuned delays
Right panel: as above, with the following differences
 beam-on-collimator events of Sep. 18

HCAL uses delays tuned from previous beam-on-collimator runs
(except a small region of the Outer calorimeter, omitted here)
LHCDM, Ann Arbor, Jan 6th - 9th, 2009
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RF Capture of the LHC Beam seen in
HCAL Endcap Energy and CMS Trigger Time
Distribution of the CMS
trigger time versus
bunch crossing (BX)
number. Before the
capture of the LHC
beam by the RF system,
the trigger timing is
spread over a few BXs.
After the capture, the
trigger timing is sharply
peaked at BX=831.
Distribution of energy observed in the CMS Endcap
Hadron Calorimeter. Before the capture of the LHC
beam by the RF system, there is a high rate of
energy deposit near the beam line. After the
capture, the beam is quite clean.
LHCDM, Ann Arbor, Jan 6th - 9th, 2009
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Evidence of Beam Gas Collisions
 Average energy as a function of
eta in the CMS Forward Hadron
Calorimeter (HF) for circulating
beam events at LHC.
 The events are triggered by
the HF from LHC's Beam 2,
which passes through the
CMS Detector from negative
to positive z.
 The events are further
selected to contain at least
one deposit of 20 GeV in a
tower which is registered by
both the long and short fiber
sections of the tower.
 The long and short sections measure the total energy and the hadronic energy of a shower,
respectively.
 The peak in energy deposition towards positive pseudorapidity is a signature of beam-gas
interactions near or within the detector, as the remnants of beam-gas interactions will have a
small transverse momentum and a larger longitudinal momentum from the initiating proton.
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Beam Halo vs. Cosmic Muons
Beam Halo Muon
in CSC and HCAL
Beam Halo
Muons

Cosmic
Muons
 Distribution of the angles of reconstructed muon tracks with respect to the plane
perpendicular to the beam.
 Beam halo muons typically make a small angle (blue histogram).
 Muons from cosmic rays pass through the cathode strip chambers at a more oblique
angle, as seen when the beam is off (black histogram).
 When the beam is on (orange-shaded histogram) the distribution consists of two
pieces, one of which closely resembles cosmic rays, and the other which matches the
beam halo simulation.
 The normalization of the blue and black histograms are not based on any calculation;
they are meant to guide the eye.
LHCDM, Ann Arbor, Jan 6th - 9th, 2009
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Beam Halo Hit Distribution
ME1
ME+1
ME2
ME+2
ME3
ME+3
ME4
ME+4
 Hit distribution in the Cathod Strip Chambers
 Red arrows indicate the order beam traversed endcap disks
 A few chambers are being fixed during the winter shutdown
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Cosmic Run At Four Tesla - CRAFT
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CRAFT
 Four weeks of continuous running
 19 days with magnet at the operational setting of B=3.8 T
 Gained operational experience and put in evidence sources of inefficiency
 Collected 370 M cosmic events, out of
Number of cosmic events
which 290 M with B = 3.8 T. Of those with
vs. time
magnetic field on:
 87% have a muon track
reconstructed in the chambers
 3% have a muon track with strip
tracker hits (~7.5 M tracks)
 3 x 10-4 have a track with pixel hits
(~75K tracks)
 Data operation performed satisfactorily
 600 TB of data volume transferred
 Prompt reconstruction at Tier 0
completed with a typical latency of 6h
 Tier 0 to Tier 1 at average of 240
MB/s
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Entries
Tracker Performance
 On track Strip clusters S/N
ratio, corrected for the track angle
TOB thick sensors: S/N = 32
TIB/TID thin sensors: S/N =
27/25
TEC (mixed thickness): S/N
= 30
 Track hit finding efficiency
 TIB and TOB layers
S/N
Layer
 Muon momentum distribution
 high quality tracks (8 hits, one in TIB
layers 1-2, one in TOB layers 5-6)
 Partial CRAFT statistics (expected >70K
tracks at PT>100 GeV for full CRAFT)
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Tracker Alignment
 Chi Square distribution
 Using 4M tracks for alignment and 1M for
validation
 “Unaligned” is the nominal geometry
 “CRUZET” is the geometry obtained from the
B=0T runs using the Hits and Impact Point
method and survey constraints
 “CRAFTHIP” is the geometry obtained from the
Hits and Impact Point algorithm applied to
CRAFT data, including survey constraints
 “CRAFTMP” is the geometry obtained from the
Millepede algorithm applied to CRAFT data
 Mean of residual distributions
(cm)
 Only modules with >30
hits considered
 TIB 96%, TID 98%, TOB
98%, TEC 94%
 HIP algorithm : TIB RMS
= 26m TOB RMS = 28m
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Pixel Occupancy and Alignment
RMS=47m
RMS=112m
 Barrel aligned at module level (200-300 hits, 89%)
 Endcap aligned at half-disk level (8)
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Drift Tube Muon System
Data

MC
MB4
Residual Distributions

Reasonable agreement
between data and MC
after cosmic muon
arrival time fit

Sigma ~ 200 – 260 m

Sector 4 of wheel -2 is
shown here

B field degrades MB1
distribution in wheels +/-2
MB3
MB2
MB1
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Drift Tubes
Drift Velocity Along z-Axis with/without Field
 Innermost stations on outer wheels have largest radial field
 Maximum difference in drift velocity is 3%
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HCAL Barrel Muon Response
 Event selection:
 Muon track matching in DT and Tracker
 20 GeV/c < Pµ < 1000 GeV/c
 CRAFT: 200 K events
 MC:
15 K events
CRAFT
data
HB energy: signal from HB towers
corrected for muon path length in HB
Test Beam 2006
Pµ = 150 GeV/c
Mean signal = 2.8 GeV
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ECAL Barrel Occupancy
 Occupancy map of
clusters in cosmic muon
runs during CRAFT
 Avalanche photodiode
gain set to x4 the LHC
conditions.
 Clusters are seeded
either from a single
crystal or a pair of
adjacent crystals above
threshold
EB+16
EB+7
 Higher occupancy in top and bottom regions (vertical flux of cosmic rays)
 Top EB- is closer to the shaft of the CMS P5 pit
 Other modulations are due to the cluster efficiency varying with crystal light yield.
 EB+7 and EB+16 suffered from low voltage problems - being fixed.
 Empty 5x5 crystal regions are trigger towers masked from the readout.
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ECAL Stopping Power
Blue dots: CRAFT experimental data
Black line: dE/ρdx in PbWO4
Red dashed line: collision loss
Blue dashed line: bremsstrahlung radiation
 Stopping power for cosmic muons as a function of their momentum
 Muon momentum is measured in the tracker
 The ECAL energy deposit is measured by the cluster energy matched to the track
 The track length in ECAL is estimated from track propagation inside ECAL crystals
 Loose selection on the track distance of closest approach to the centre of CMS
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Activities for and after winter shutdown
 Detector opening started on Nov 17th
 Started a selected list of interventions/repairs for problematic channels
(order of the percent)
 CMS cooling system maintenance (done)
 Installation of Preshower detector in February
 Continue the optimization of detector operations
 Optimization of online system and procedures to eliminate possible
sources of data taking inefficiency
 Centralization and optimization of detector control system and monitoring
 Consolidation of data quality monitor and certification
 Aim to reduce the needed number of shifters and expertise to decrease
long term manpower load
 Schedule for Resuming Commissioning Activities
 Global run sessions to be resumed mid-Feb
 First CRUZET (Cosmic RUn at ZEro Tesla) in April
 Detector closed around mid-May 2009
 Extended CRAFT (Cosmic Run At Four Tesla) before LHC beam
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Paolo Rumerio, Maryland
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Conclusions
 A long, intensive and challenging installation and commissioning campaign was carried
out successfully
 All major components of the detector have been installed and commissioned
 Preshower detector will be installed in February
 CMS was ready for beam
 Collected and exploited at best the beam data delivered before the September 19th
incident
 A one-month-long cosmic ray run with nominal magnetic field has been taken
 Commissioned and verified stability of operations (detector, magnet and operators)
 Pointed out inefficiencies and issues to be addressed
 Some interventions on detector components are currently being carried out
 none of the problems being worked on would have prevented efficient data taking if
collisions had been delivered
 Schedule for this year has been defined
 It will evolve with time, depending on ongoing repair activities and progresses made
 Commissioning activities will resume by the end of this month. The goal is to
optimize performance, increase efficiency and reduce manpower and expertise
needed in control room
 CMS will be closed again with enough contingency for being ready for beam,
allowing another extended cosmic ray run with magnetic field
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