1. Status and startup for physics with LHCb
G. Passaleva
(INFN-Firenze)
On behalf of the LHCb collaboration
CERN June
HERA-LHC Workshop

2. Outline The LHCb experiment LHC startup scenario Commissioning plans
Detectors
Trigger
Expected performance
Detector status
LHC startup scenario
Commissioning plans
First physics measurements
Conclusions
Remind the main features
I will discuss what we believe should be at LHCb the LHC startup steps and sketch the plans concerning the commissioning of the experiment
Finally I will briefly discuss a few physics measurements that we believe we can perform with the very first data. These are of course a small part of the very rich and complex
Physics program of LHCb that will extend over the first 5 years of LHC and that I’ll not have time discuss here.
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3. pp interactions/crossing
LHCb environment
Forward peaked, correlated
bb pair production 
LHCb is a forward spectrometer
2.0 < || < 5.3
100 mb
230 mb
L tuneable by defocusing the beams
Choose to run at <L> ~ 21032 cm–2s–1 (max. 51032 cm–2s–1)
Will be available from 1st physics run
Clean environment (n = 0.5)
2 fb–1 / year
Lhcb is dedicated th b physics b pairs are produced in the forward region in a correlated way therefore lhcb is a forward spec. covering
The region of rapidity between 2 and 4.5
2 fb-1in stable conditions
pp interactions/crossing
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4. The LHCb spectrometer
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5. (visible bunch crossings)
Trigger
10 MHz
(visible bunch crossings)
Level-0:
pT of
m, e, h, g
Calorimeter
Muon system
Pile-up system
1 MHz
HLT:
Confirm level-0
Associate Pt/IP
Full event reconstr.
Inclusive/exclusive
selections
Full detector
information
2 kHz
L0: custom hardware
HLT: CPU farm
Output rate
Event type
Physics
200 Hz
Exclusive B candidates
B (core program)
600 Hz
High mass di-muons
J/, bJ/X (unbiased)
300 Hz
D* candidates
Charm
900 Hz
Inclusive b (e.g. bm)
B (data mining)
As the experiment is dedicated to b physics whose xsection is only 0.5 mb over a thotal pp x section of 200 mb, a very specialised trigger is mandatory
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6. Expected performance Bd Bs Comb. D2 4-5% 7-9%
Full detector simulation based on Pythia and GEANT4
Full pattern recognition implemented:
Track finding efficiency: ~ 95% for long tracks p > 10 GeV/c
Momentum resolution: 0.4%
Mass resolution: ~ 14 MeV/c2 for B mesons
Secondary vertex resolution ( in z): ~ 170 mm
Proper time resolution for B decays: ~ 40 fs
st1 = 33 fs
st2 = 67 fs
Bs→Dsp
proper time
(31%)
Flavour tagging efficiency Bd Bs
Comb. D2
4-5%
7-9%
The momentum resolution is at the level of 4 per mill for high pt tracks
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7. Neutral reconstruction
Particle ID
/K separation provided by RICH for 2<p<100 GeV:
<(KK,p)> = 83%
<(K,p)> = 6%
Clean separation of two-body B decays,
e. g. B 
Neutral reconstruction
Good efficiency for 0 in B0 + - 0, using both resolved and merged clusters in the ECAL
Modes with multiple neutrals (0, , KS,…) will be challenging at LHCb
(m)=12 MeV
Efficiency ~53%
Merged 0
The PID capability of LHCb is a unique feature among the LHC experiments and is based mainly on the rich system
We are able to separate very cleanly pi from k with p from 2 to 100 gev with obviuos benefits as illustrated in the plots
Concerning the neutral particle, we have a reasonably good reconstruction efficiency for pi0s etas and so on. However modes with
Multiple neutrals are challenging for lhcb
Resolved 0 
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8. Detector status: a snapshot from the pit
In the pit
To be installed
Muon System
Calorimeters
RICH2
Tracking system
Magnet
RICH1
Vertex Detector
So long for the detector features. In this picture you can see what happens in hese days in the lhcb pit. In red you have the subdetectors already
Installed while in green is what is still missing. As you can see almost all the subdetectors are already in place
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9. Muon system support walls
All four panels M2-M4 installed.
87% of muon chambers built
Rolf Lindner 01/06/2006
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10. Muon chamber supporting wall from top
Rolf Lindner 01/06/2006
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11. Outer Tracker installation
Rolf Lindner 01/06/2006
Arrival of Outer Tracker support structure April ‘06
18 m
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12. Vertex detector installation
Rolf Lindner 01/06/2006
The vacuum tank of the vertex detector is lowered into the pit…
…and installed in front of the RICH I magnetic shield (in blue)
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13. LHC both sides of the IP8 IP8 POINT 7 POINT 1 CERN June 6-9 2006
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14. Detector status: details
Magnet: installed & mapped
Vertex detector: Vacuum tank being installed; silicon modules in production; installation at beginning of 2007
Tracking system: Production almost complete; installation in the pit will end in fall 2006
Calorimeters: installation finished, commissioning ongoing
RICH System: RICH I shielding installed, installation completed by fall 2006; RICH II in the pit, installation ongoing
Muon system: 85% of chambers produced; installation in progress
ON/OFF-line software: is progressing well
This is in more details the status:
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15. Detector status
Plan to have everything installed by the end of 2006/beginning of 2007
Aiming to have the complete experiment ready for data taking in 2007
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16. LHC startup scenario (from the LHCb point of view)
From the LHCb point of view this would be a desirable scenario:
2007: detector alignment and calibration, possibly already with J/y signals from pp collisions
2008: 0.5 fb-1
2009: 1.0 fb-1
2010: 1.5 fb-1
i.e. ~3 fb-1 by the end of 2010 at the required average luminosity of ~2x1032 cm-2s-1
These were the latest news about detector installation. Let’s come now to discuss the LHC startup steps at LHCb
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17. Commissioning plans Global commissioning without beam in 2006 - 2007
Commission the subdetectors (starting now !)
Test the DAQ
Test the electronics calibration procedures
Check the scalability of the system, improve when needed
Use of circulating beam in summer 2007: LHCb is a forward detector, cosmics can not help: beam-gas gives useful tracks for time and position alignment. Study of beam gas events ongoing: useful also for measuring and monitorng the luminosity (cross section measurements! See M. Ferro-Luzzi contribution to this workshop)
Pilot Run (low luminosity)
􀁺Without magnetic field: (time and space) alignments
􀁺With magnetic field: Trigger setup and start collecting data
Given this scenario, we are defining the plan for the detector commissioning
Once we know that we readout the data from the same crossing, aligning the detector is the next
important step, which is needed to get the HLT trigger working. As indicated earlier, the first
collisions will be probably with magnet OFF, and will be used to collect straight lines. The Velo
internal alignment should come from the 2006 test beam, and should give a very good starting
point for aligning the other detectors. This alignment is essentially an analysis task, as there is no
configuration of the detector to change after alignment. Collecting enough data will be the main
requirement to the commissioning activity. If corrective actions are needed on the detector
position, they will have to be performed during a long enough access, this means most probably
after the Pilot Run.
Once we know that we readout the data from the same crossing, aligning the detector is the next important step, which is needed to get the HLT trigger working. As indicated earlier, the first collisions will be probably with magnet OFF, and will be used to collect straight lines. The Velo internal alignment should come from the 2006 test beam, and should give a very good starting point for aligning the other detectors. This alignment is essentially an analysis task, as there is no configuration of the detector to change after alignment. Collecting enough data will be the main requirement to the commissioning activity. If corrective actions are needed on the detector position, they will have to be performed during a long enough access, this means most probably after the Pilot Run.
As soon as possible in the commissioning of the LHC, and once we have done the basic time alignment, we should ask for collisions with our magnet ON. This is mandatory to start working on the software trigger, and validating the simulations. This is also needed to commission the Level-0 muon trigger. As the luminosity will be very low, with a single bunch colliding in LHCb, a simple Level-0, with some downscaling if needed, will select events useful for understanding the trigger and start working on reconstruction. The HLT should be run in ‘monitoring’ mode, this means writing its decisions into the event buffer, but accepting all events. Gradually, rejection can be enabled once the proper behaviour of each stage is validated.
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18. Preparing for physics…with 0.1 fb-1 of data
Use special samples (mainly from inclusive HLT) for recontsruction and PID calibration and tuning: J/   for m ID D* D0(Kp)p for K/p ID and m mis-ID
B0D* 3 hours of data-taking
events after triggerxSelection (0.1 fb-1):
B+ J/()K  80 k
B+ D0(*) n  100 k
B0 D*+n  350 k
Bs  Ds(*)mn  50 k
sw/w 1-2 % per tagger
Use B+/B0 control channels for tagging tuning
From the physics side, the commissioning consists essentially in the calibration and tuning of reconstruction pid and taggingalgorithms
This is done in a few steps:
As you can see with a very short amount of datat taking time we can observe very well the time dependent asymmetries
With ths statistics we can estimate the mistag rate with 1-2% uncertainty
Use B0 control channels for oscillation measurement, as a first check of tagging performance.
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19. First physics measurements
LHCb physics program with the very first data:
J/y production studies (e.g. prompt vs B J/yX, bb cross section)
sin(2b) (as a proof of principle of CPV measurements)
Dms and fs (after CDF Dms, measurement, recent theoretical papers indicate fs measurement as very interesting for NP)
Bsmm
We have seen uptoknowwhat we shoulddo to have the experiment ready for physics.let’s now go through a few physics measurements tha can be performed with, say, 0.5 fb-1 and that we consider particularly interesting at the startup. Among these measurements I included
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20. J/y production studies
LHCb will record a very large sample of J/y
s(J/y prompt) = mb s(J/y from B) = 11 mb
Inclusive HLT rate  600 Hz
True J/y rate  130 Hz
109 J/y per year
First preliminary studies on bb production cross section using B  J/y decays are ongoing
ATLAS/CMS will measure || < 2.5
ALICE will measure || < 0.9 and 2.5 < || < 4
LHCb will measure 2.0 < || < 5.3
An unbiased sample of J/psi is selected by the inclusive dimuon hlt.
…..dominated by prompt J/psi
Notice that a/c can measure the x section in the regionof eta <2.5,… while LHCb….
LHCb measurement of bb will allow a test of QCD in new region of phase space.
Not really for the very first data ! A rough measurement would be iteresting anyway
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21. J/y production studies
Generator studies
Detailed generator studies on quarkonia production are ongoing.
First preliminary results give large inconsistency between our standard PYTHIA settings (v 6.3) and version 6.4 where NRQCD model has been introduced for heavy quarkonia production:
s(J/y prompt) ~ 3 times lower (See M. Bargiotti talk at this workshop for details)
 even a rough measurement of the ratio of prompt J/y vs J/y from B will be very interesting at the very beginning
We are also doing an accurate generator study of geipsai production.
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22. sin(2) with B0J/ KS
Expected to be one of the first CP measurements:
ACP(t) (background subtracted)
Demonstrate tagging performance and ability for CP physics
Sensitivity:
LHCb expects ~60k signal events for 0.5 fb-1  stat(sin(2)) ~ 0.04
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23. Bs mixing: ms
1 year (2 fb–1)
ms= 20 ps-1
Bs  Ds- p+
(t)~40 fs
LHCb
CDF results with 1 fb: 3.7k fully reconstructed Bs  Ds–+, Ds–3 ~85 fs, D2 = 5 % ~3 significance at ms~17 ps
CDF measurement is already statistically very precise (~2%)
LHCb expects: 120k BsDs evts/year (2 fb–1) B/S = 0.4,  ~ 40 fs, D2 = 9 %
LHCb can reach Tevatron (statistical…) precision in the first months of data taking.
Note also that as ms~17 ps, the ultimate  of LHCbis not essential.
ms is in any case needed for fs measurement
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24. fs and DGs from BsJ/ Bs J/ is the Bs counterpart of B0J/ KS:
Bs mixing phase fs is very small in SM: fs = –arg(Vts2)=–22 ~ –0.04  sensitive probe for new physics
Sensitivity (at ms = 17.5 ps–1):
131k Bs J/ signal events/year B/S=0.12
stat(sin  s) = 0.023
stat(s/s) ~ (1 year, 2 fb–1)
Recent theoretical works indicate that large values of fs are not excluded:
 already with 0.2 fb-1 set an interesting limit or measure it if large,
J/ final state contains two vectors:
angular analysis needed to separate CP-even and CP-odd
Fit for sin fs, DGs and CP-odd fraction (needs external ms)
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25. Constraints on NP from s measurement
Constraints on NP contribution to fs
(from hep-ph/ )
>90% CL
>32% CL
>5% CL
After LHCb measurement of s with (s)= ±0.1
(~ 0.2 fb–1)
UT fit collaboration estimate for s (hep-ph/ )
SJyf = sin(2c-2qs) = 0.07 ± 0.49 ss
These are two examples of these analyses that I give you as a reference
courtesy Z. Ligeti hs
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26. Inclusive bb background
Bs  +–
Very rare decay, sensitive to new physics
BR ~ 3.5  10–9 in SM, can be strongly enhanced in SUSY
Current limit from Tevatron:
D0: 2.310–7 at 95% CL
CDF: 1.010–7 at 95% CL
LHCb has prospect for significant measurement but difficult to get reliable estimate of expected background:
Full simulation: 10M incl. bb events + 10M b, b events (all rejected)
1 year
Bs – signal (SM)
b, b background
Inclusive bb background
All backgrounds
LHCb
2 fb–1 17
< 100
< 7500
Finally a few words about the rare decay …..
In principle a (lucky !) measurement is possible already with 0.5 fb-1
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27. Conclusions
Construction of LHCb is well advanced: we plan to complete the installation by the end of 2006 aiming to have the full detector ready for data in 2007.
Commisioning strategy is being prepared in detail
Strategy for calibrations, alignments, trigger and analysis tuning being devised
Already with the very first data very interesting measurement can be performed: I invite you to follow the startup of our experiment !
This is all I wanted to present, thanks for your attention
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HERA-LHC Workshop