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Status of the LHCb experiment
Andrei Golutvin ( Imperial & CERN & ITEP )on behalf of the LHCb Collaboration
Outline:
Introduction Detector Subsystems Trigger/Online/Computing First Look at the data Cost and funding issues Collaboration matters Preparation for LHCb upgrade Physics goals in 2010
RRB April 2010 1
2
Commissioning of LHCb with data was the main activity since last RRB
Detector is time aligned to optimal working point within 1–2 ns. Data taken with and without magnetic field for position alignment
A total of 300k collision events at 900 GeV recorded in 2009. Overall operation went very smoothly. Due to beam optics Vertex Detector (VELO) modules can approach only ±15 mm from the beam. The VELO powering and closing procedures have been optimized and commissioned In 2010, from first collisions onwards, LHCb is taking successfully data at 7 TeV with high efficiency LHCb is in excellent shape for the Physics Run in 2010-2011
RRB April 2010
Brief Summary
LHCb Collaboration
3RRB April 2010
730 members15 countries54 intitutes
VErtex LOcator (CH,DE,GB,NL) 2×21 pairs of Si sensors arranged in 2 halves; each pair consists of one sensor with R-
and one sensor with -strips
4RRB April 2010
99.3% of channels operational– For first collisions at 900 GeV VELO was operated in a safe
mode utilizing an “incremental” powering scheme. VELO was
powered in its open position and then each half moved to within 15 mm of the nominal physics position (full closure possible only above 2 TeV /beam)
– Primary vertex distributions from
both beam-beam and beam-gas
events
– The module alignment is stable
within 4 μm. Two halves relative
position is aligned to better
than 30 μm, as evaluated with
2009 and 2010 data
RRB April 2010 5
When running at 3.5 TeV per beam VELO has beensuccessfully closed
During closing procedure
• The distance between two VELO halves has been measured using reconstructed primary vertices at each step of the 1st closing with beam
• Closing procedure works well ( takes ~ 15 min now ) Will be further improved !
Reconstructed distance between VELOhalves as a function of time during 1st closure
RRB April 2010 6
Status of VELO replacement• All 42 hybrid replacement modules have been built and tested Burn in programme in Q2 2010
• The replacement mechanics is expected to be completed by October 2010
• Complete VELO replacement halves are planned to be ready for the LHC start in 2011
RRB April 2010 7
Outer Tracker – OT (CERN,CF,CN,DE,NL,PL)Three stations with each 4 stereo layers of straw tubes 5 mm diameter and 5m length; 55k channels
OT
CaloMuon
• Detector is 100 % efficient and running with low noise at the nominal threshold. All Front-End spares are available
• In order to improve aging behavior a 1.5% fraction of O2 has been added to the gas mixture. Aging tests in situ show mitigating effect of O2 and a general improvement with flushing time. Furthermore the possibility of curing gain losses in situ by means of HV training procedure has been demonstrated
One of the first LHCb collision events @ 3.5 TeV per beamregistered on March 30
RRB April 2010 8
Drift-time space relation (R(t))
R(t) from test beam R(t) from fit to proton data
R
Plateau efficiency 98.7 %
R [mm]
Hit residuals:
Data/MC differences due to missing module alignment
straw tube
OT performance:
Without O2 @ 450 GeVWith O2 @ 3.5 TeV
No effect caused by addition of O2
Cell efficiency profile:Efficiency vs. distance in mono layer plane
ST: Tracker Turicensis & Inner Tracker(CERN,CH,DE,ES,UA)
TT covers area of 1.41.2 m2; 4 stereo layers with ladders consisting of 3 or 4 chained Si- sensors with strip pitch 183 micron; 143k channelsIT: 3 stations with 4 boxes each arranged around beam pipe; each box has 4 stereo layers x-u-v-x, modules with one or two chained Si-sensors; strip pitch 198 micron; 130k channels
RRB April 20109
• Both TT and IT run smoothly and without problems (> 99.5% of TT channels and 99% of IT channels are operational)
• Significant progress in improving stability and reliability of the control and monitoring software
• The problem of breaking bonds on the TT hybrids has stabilized. No new broken bonds since May 2009. New hybrids are being ordered and the nine affected modules will be repaired
• Internal alignment of IT has been verified with beam and a global alignment relative to the other tracking components performed
RRB April 201010
TT and IT performanceσ = 77.3µm
unbiased residual σ~72μm
TTUnbiased TT residuals is still broader thanexpected in MC (49 μm). Further improvementwill be achieved soon
IT tracks and efficiencies (alignment fixed from TED data)
IT• Unbiased residuals (2009 data) still show room for improvement (expect ~ 50 μm)
• Efficiencies O(98%)
RRB April 201011
Demonstration of tracking performance with reconstructed particles
Ξ from ~ 65 µb-1
Λ from ~ 65 µb-1KS from ~ 65 µb-1
RICH (CERN,CF,GB,IT)RICH1 and RICH2 with 3 radiators covers momentum range 2-100 GeV; RICH1: 5cm aerogel with n=1.03 & 4m3 C4F10 with n=1.0014; RICH2: 100m3 CF4 with n=1.0005;
~500 HPD to readout
RRB April 201012
Both RICH1 and RICH2 take data with great success
• RICH2 was fully aligned. For RICH1 more data are required to align the mirrors in the outer region from where aerogel rings are reflected. Also some indication that the poor resolution for the aerogel rings is due to low photon yield.
• Evolution of each HPD lifetime using ion feedback is continuously monitored. In March those tubes predicted to glow in 2010 have been replaced with refurbished ones. The repair process is proceeding regularly and the extracted tubes are being sent to PHOTONIS.
• Satisfactory stability of HV system and gas system
• PID performance has been calibrated using kinematically reconstructed Ks mesons and Λ hyperons.
RRB April 2010 13
after alignment
momentum spectrum
before alignment
RICH 1LHCb data(preliminary)
Kaon ring
RICH 2LHCb data(preliminary)
Kaon ring
Orange points photon hits Continuous lines expected distribution for each
particle hypothesis (proton below threshold)
PID with RICH
RRB April 2010 14
Demonstration of RICH PID performance with reconstructed particles
Φ from ~ 65 µb-1
K* from ~ 65 µb-1
Calorimeters (CERN,CF,ES,FR,RO,RU,UA) PS/SPD: 12k scint. tiles readout by WLS; ECAL:
6k shashlik cells; HCAL: TILE Calo, 1.5k channels
15RRB April 2010
The four calorimeter systems operate very effectively providing the principle trigger for LHCb
• Initial time alignment has been significantly improved. The current inter-cell time alignment is 1 ns for HCAL/ECAL and 2 ns for PS/SPD
• Energy calibration is being gradually improved using collected data. Inter-calibration at the start-up was close to 9% for ECAL, <4% for HCAL and ~15% for PS
• The reconstructed masses and widths of the 0 andsignals agree well with expectations. In order to reach ~1% calibration accuracy for ECAL and PS one needs ~50 M events.
RRB April 2010 16
π0
<m> = (135.0±0.6) MeV/c2
σ = (10.9±0.7) MeV/c2
Et(γ)> 300 MeV; Et(di-γ)> 2 GeV
η
<m> = (547±5) MeV/c2
σ = (24±3) MeV/c2
N(πº)=849±36N(η)=146±32R(η/ πº)=17.2±3.8 %
N(πº)=719±31N(η)=163±27R(η/ πº)=22.7±3.8 %
2009 data Monte Carlo
2009 data 2009 data
MeV/c^2
Et(γ)> 500 MeV; Et(di-γ)> 2 GeV Et(γ)> 500 MeV; Et(di-γ)> 2 GeV
Et(γ)> 300 MeV; Et(di-γ)> 2 GeV
Demonstration of CALO performance with reconstructed particles
Muon (CERN,CF,IT,RU)Arranged in 5 SuperLayers; M1 consists of 12 double triple GEM
chambers and 264 MWPC’s; M2-M5 consists of 1104 MWPCs
17RRB April 2010
• The Muon system operates successfully, both the efficiency and the noise level are in perfect agreement with expectations from the test beam
RRB April 2010 18
• Muon detector hardware performs very well:
- Only ~0.1% chamber gaps showed some HV problems - <0.1% dead readout channels - Negligible number of noisy channels
• Time alignment in perfect agreement with expectations
• Space alignment: analysis of collision data taken in 2009 confirmed ~7-8 mm shift in X of M4 A-side that was seen with cosmics M4 position was corrected in January 2010
• Stability of HV modules is of some concern. Full review of the HV control system has been made and some hardware modifications have been applied to the CAEN power supply system to achieve more reliable operation
MUON performance
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Strategy for trigger settings in 2010
RRB April 2010
Few fills at injection energy 450 GeV, 2-4 bunches 5·1010 p colliding,
β * =10 => rate ~(few) 100 HzRamp in energy 3.5 TeV, 2 bunches 1·1010 p colliding,
β*=10 => rate ~100 Hz
Squeeze of β* 3.5 TeV, 2 bunches 1·1010 p colliding, β* = 2 => rate ~500 HzIncreased bunch charge 3.5 TeV, 2 bunches 5·1010 p colliding,
β*=2 => rate ~10 kHz
Increasing number of bunches 3.5 TeV, 19 bunches 5·1010 p colliding,
β*=2 => rate ~100 kHz
mbias triggers based on Level 0 objects: muon pT, hadron pT, Pile-Up System
L0 and HLT optimized for prompt Charm and Beauty
+ (mbias & random triggers) downscaled
Optimized for Beauty Physics
Prompt charm efficiency increased by more than a factor 4 w.r.t. design settings without loss in b-physics
Evo
lutio
n of
lum
inos
ity in
firs
t few
mon
ths
When moving to crossing angle and 50 ns bunch spacing we expect L~1-
2·1032 cm-2s-1 with ~200 pb-1 in 2010 and ~1 fb-1 in 2011
(~1/2 of a nominal year for LHCb)
RRB April 2010 20
Online & Computing
• Data monitoring and online reconstruction are commissioned and in regular use Some minor problems with the switches of the read-out network, which are addressed by the manufacturer with high priority
• Completion of the HLT farm to its full capacity is foreseen towards the end of 2010 depending on the LHC luminosity progress
• Data processing chain works well. New data are distributed to the LHCb Tier1s, fully reconstructed on the Grid and made available for analysis within a few hours.
• Three reprocessing done so far on the Grid, each taking less than one day
• Simulation campaign to prepare the 2010-2011 analyses of data at 3.5 TeV started
• Some concern with Tier1s stability in particular regarding Storage and Data Access CERN site busy with user analysis
RRB April 2010 21
D0→Kπ from ~110 µb-1
D+ →Kππ from ~110 µb-1
Towards LHCb physics programme
First D mesons havebeen reconstructed !!!
RRB April 2010 22
J/ψ from ~160 µb-1
RRB April 2010 23
23
B+→J/ψK+ candidate: global view(muons are magenta, kaon is red)
4 J/ candidates have non-zero proper time as expected for production in B decays BJ/
>25 separation between primary and secondary vertices
First candidate for reconstructed B meson
RRB April 2010 24
Primary vertex
B decay vertex+
-
K+
J/ψ
B+
[x 0.2mm]
[mm]
YZ Projection
Tracks from primary vertex
B→J/ψK candidate: YZ vertex zoom
RRB April 2010 25
Cost and Funding
Collaboration Matters• Two new institutes accepted as Technical Associates: - Catholic University of Rio de Janeiro, Brazil - Tier-1 centre CCIN2P3, Lyon, France
• Guy Wilkinson (Oxford) is the Physics Coordinator for a term of 1 year as from January 1, 2010 • Rolf Lindner has been appointed as the Technical Coordinator for a term of 3 years starting from July 1, 2010
• Marco Cattaneo (CERN) has been appointed as the Computing Project Leader for 2 years starting from January 1, 2010• Chris Parkes (Glasgow) has been appointed as the Vertex Detector Project Leader for 2 years starting from June 15, 2010
• Overall situation is healthy; no cash flow problem foreseen
• VELO replacement financing mechanism works well
• Prepare for important interventions on sub-detectors and infrastructure during long shutdown in 2012
RRB April 2010 26
LHCb Upgrade activities
A Letter of Intent for the LHCb upgrade is under preparation
The strongest part of the LHCb physics case is the flexibility to be preparedfor the exploration of New Physics
Staged approach:
First stage – Full software trigger
- Upgrade to 40 MHz readout keeping sub-detectors unchanged wherever is possible
- Construct NEW VELO
RRB April 2010 27
Expected B-physics reach in 2010-2011
Sensitive probe for MSSM with large tanβ: Br (BSμ+μ-) ~ tanβ6 / MA
4
Large (non-SM) phase favoured by D0 and CDF analysis:Φs [ −1.47 ; −0.29 ] [ −2.85 ; −1.65 ∪] (90% CL range)
Assume ~200 pb-1 in 2010 and ~1 fb-1 in 2011
2010
2011
Exclusion limit @ 90% C.L.
2010 20
11
28
Conclusion I LHCb is successfully taking data with high efficiency !!!
RRB April 2010
LHCb operation over 30/3-13/4
17%
69%
8%1% 5%
Tech Velo closed Velo open DAQ Others
On the ~82 hours of collision delivered
-Technic program completed at 95%
- 98% DAQ efficiency -95% detector efficiency
-Velo closing efficiency 94% - Mostly in beginning - Long fill help
In 2010 we have so far recorder ~14M collisions at √s = 7 TeV
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First data are being used for calibration of the detector and trigger in particular. - First results of low Pt physics are available at LHC energies
- Some high class measurements in the charm sector may be possible with 50 pb-1. Charm resonances have been reconstructed.
With ~ 200 pb-1 data sample LHCb will reach Tevatron sensitivity in a few golden channels in the beauty sector
Further consolidation is important prerequisite for efficient long term operation (e.g. R&D on improved reliability
of readout cards in EPFL)
RRB April 2010
Conclusion II
RRB April 2010 30