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NIKHEF Jaarvergadering, 21-22 Dec. 2005 1/19 Physics Studies and Track Reconstruction in LHCb at NIKHEF E. Rodrigues, on behalf of the NIKHEF–LHCb group.

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Presentation on theme: "NIKHEF Jaarvergadering, 21-22 Dec. 2005 1/19 Physics Studies and Track Reconstruction in LHCb at NIKHEF E. Rodrigues, on behalf of the NIKHEF–LHCb group."— Presentation transcript:

1 NIKHEF Jaarvergadering, Dec /19 Physics Studies and Track Reconstruction in LHCb at NIKHEF E. Rodrigues, on behalf of the NIKHEF–LHCb group  CP violation / B physics - general introduction  LHCb experiment - basics - LHCb NIKHEF  Physics (preparation) studies - NIKHEF contributions  Tracking / Reconstruction - group’s involvement NIKHEF Jaarvergadering 2005

2 NIKHEF Jaarvergadering, Dec /19 CP Violation in the B Sector Origin of CP-Violation in the SM: CKM Matrix complex and unitary 4 parameters: 3 Euler angles 1 Phase CP Violation 1 Re 0  Im Re  0 Im    Re Unitarity Triangle(s) VV + = V + V = I

3 NIKHEF Jaarvergadering, Dec /19 (side view) pp collision Acceptance 10 mrad 250/300 mrad LHCb Detector Single Arm Forward Spectrometer « Tracking » detectors

4 NIKHEF Jaarvergadering, Dec /19 The NIKHEF LHCb reconstruction / tracking / software “team” 2005: – – Staff: Th. Bauer, H. J. Bulten, M. Merk, G. Raven – – Post-docs: E. Rodrigues (CERN based), J. v. Tilburg, N. Tuning – – Graduate students: J. Amoraal, E. Bos, B. Hommels, B. M’charek, J. Nardulli, G.Ybeles Smit, M. Zupan – – Undergraduate students: S. Cohen NIKHEF software activities embedded in: – – The LHCb Computing Project (E. Rodrigues responsible for “Track Fitting”) – – The Physics Planning Group (G. Raven convenor of “Proper time and mixing” WG) Tracking / Reconstruction / Physics

5 NIKHEF Jaarvergadering, Dec /19 NIKHEF – LHCb Group (part of) Practicing Team building Barcelona 9/’05 After Jeroen’s promotie 10/’05

6 NIKHEF Jaarvergadering, Dec /19 Master & PhD Theses in 2005 Jan Amoraal Sander Klous Besma M’charek Jeroen van Tilburg … after the promotie in Oct. ’05 ! Thesis “Track simulation and reconstruction in LHCb” Thesis “LHCb: vertex detector and read out chip, computing challenge and B s -> J/   ” 2005 PhD Post-doc … off to Zűrich in ‘06 Jan June Dec Master PhD ATLAS Next PhD’er on the pipeline: Bart Hommels... … has already a job in Cambridge! PhD Master

7 NIKHEF Jaarvergadering, Dec /19 Physics Studies B 0 s  D s  B 0 s  J/  (μ + μ - ) K +,* B 0 s  μ + μ -  m s Marcel Merk Gerhard Raven Jeroen van Tilburg B 0 s  D s K Commissioning / lifetimes Gerhard Raven Peter Vankov B 0 s  J/  (μ + μ - )  Rare event New physics N. A. … yet … B  X s μ + μ -  Thomas Bauer Shirit Cohen Besma M’charek Marcel Merk Eduardo Rodrigues Jeroen van Tilburg  s  Jan Amoraal Sander Klous Gerhard Raven + approved projectruimte (post-doc + grad. student) New physics Marko Zupan Year 1 > Year 1

8 NIKHEF Jaarvergadering, Dec /19  s from B 0 s  D s  Decays Marcel Merk Gerhard Raven Jeroen van Tilburg MC truth Reconstructed If  m s = 25 ps -1 B s mixing can be clearly observed in B s  D s    with one year of data taking Once oscillation observed,  m s can be measured with very high statistical precision  m s )=0.01ps -1 msms 20ps -1 25ps -1 30ps -1 sensitivity in one year: ( assuming 55  <  <105  ) LHCb in pole-position for  m s : - Excellent vertex resol. and proper time resol. proper time resol. mm

9 NIKHEF Jaarvergadering, Dec /19  from B 0 s  D s K Decays Thomas Bauer Besma M’charek Marcel Merk Jeroen van Tilburg ( taking  m s = 20 ps -1 NIKHEF: - Responsible for the selection strategy - Drives the sensitivity studies N.B.: we were amongst the first to use the Grid for these sensitivity studies! t rec 5 years data: B s → D s -   B s → D s - K +  m s = 20 ps -1 )

10 NIKHEF Jaarvergadering, Dec /19 B 0 s  J/  +  -  Decays Jan Amoral Sander Klous Gerhard Raven “golden decay”, theoretically clean“golden decay”, theoretically clean Measurement of  angle and  sMeasurement of  angle and  s - very small in SM: sin 2  = very small in SM: sin 2  = any large asymmetry means new physics - any large asymmetry means new physics If  s  s is ~0.1, can do a 5  discovery in one year,If  s  s is ~0.1, can do a 5  discovery in one year, almost independent of specific parameters Time for 5  discovery of new physics in B s mixingTime for 5  discovery of new physics in B s mixing depends on the size of the new physics contribution… B s  J/ψφ (B s tagged)  Proper time τ (ps) Such an observed distribution would mean new physics … LHCb annual yield ~ 120k events!

11 NIKHEF Jaarvergadering, Dec /19 Inclusive B  X s  +  -  Decays Marko Zupan Goal:  Study of inclusive b -> s      decays Theoretical interest:  Rather sensitive to new physics via loops (e.g. SM vs SUSY) Experimental aspects:  BR ~ … too low for B-factories …  In practice X s is made “as inclusive as possible”  Annual yield ~ 9000 events! Forward-backward asymmetry A FB (s) s=M(  +   ) 2 [GeV 2 ] SM diagrams

12 NIKHEF Jaarvergadering, Dec /19 Tracking / Reconstruction NIKHEF “software” group Group’s involvement in … OT event model & alignment studies:  NIKHEF responsibility Tracking event model :  NIKHEF responsibility  Driving force Pattern recognition:  Many contributions: seeding, fast (online) seeding, matching Track Fitting :  NIKHEF responsibility Magnetic field map:  Participation in B-field map measurements  Responsible for including the real field map in software, for physics

13 NIKHEF Jaarvergadering, Dec /19 Tracking Strategy in LHCb A typical event:  26 long tracks  best quality for physics: good P & IP resolution  11 upstream tracks  lower p, worse p resol., but useful in the RICH1 pattern recognition  4 downtream tracks  improves K s finding efficiency (good p resolution)  5 seed/T tracks  used in the RICH2 pattern recognition  26 VELO tracks  used in primary vertex reconstruction: good IP resolution |B| (T) Z (cm) B-field measured to ~ 0.03% precision!

14 NIKHEF Jaarvergadering, Dec /19 Marko Zupan - L1 VELO tracks + L1 muon seeds + binary tracker hit date binary tracker hit date - Moderate efficiency ~30% obtained but very high rate reduction ~400! very high rate reduction ~400! - Peak resol. < 100 MeV - Promissing trigger for calibration data … under further study … under further study … L1 tracking Online Pattern Recognition L0 tracking Bart Hommels Niels Tuning J/  mass the L1 trigger  Pile-up veto strategies / algorithm (and hardware) is NIKHEF responsibility  Performance & robustness studies being finalized  Pile-up veto detector can also be used for a luminosity measurement

15 NIKHEF Jaarvergadering, Dec /19 Offline Pattern Recognition Henk Jan Bulten Bart Hommels Jeroen van Tilburg Gabriel Ybeles Smit Offline tracking in numbers:  ~ 95% B-decay products found  Ghost rate ~ 3% NIKHEF contributions: - Responsible for seeding PR in the T stations - getting it ready for a realistic detector - VELO-seed matching PR maintained VELO TT T2T3T1 Efficiency for long tracks ε ~ 95% (p>5 GeV)

16 NIKHEF Jaarvergadering, Dec /19 Track Fit à la Kalman Eduardo Rodrigues Jeroen van Tilburg Benefits of the Kalman filter technique:  Mathematically equivalent to least  2 method  Adds measurements recursively starting from a initial track estimate  Reconstructs tracks including multiple scattering and energy losses Ongoing work: - Adapting fit for a realistic detector … Note: Fitted with single Gaussian in each bin Reconstructed tracks Ideal tracks prediction step filter step Momentum resolution ~ 0.35%

17 NIKHEF Jaarvergadering, Dec /19 Tracking in a Realistic Detector Edwin Bos Marcel Merk Gerhard Raven Eduardo Rodrigues Jeroen van Tilburg Warped TT sensors “banana-shaped” Outer Tracker modules Needs:  Tracking in a realistic environment: move away from ideal MC to real world move away from ideal MC to real world tilted and/or deformed detectors tilted and/or deformed detectors deal with misalignments deal with misalignmentsIdea:  Use the concept of “trajectories” developed in BaBar a track’s trajectory can be approximated locally a track’s trajectory can be approximated locally as a parabola as a parabola one could also parameterize locally a detector one could also parameterize locally a detector element with a measurement (hit) as a element with a measurement (hit) as a parabola, whatever the shape of the whole is parabola, whatever the shape of the whole is  Track fit is then “reduced” to a à la Kalman minimization of distances between local parabolic trajectories approximations!  track fit blind to details of detector shapes and misalignements

18 NIKHEF Jaarvergadering, Dec /19 In short …  Excellent group spirit  Lots of interesting, exciting and fun work  Heavy involvement in a variety of complementary aspects of LHCb preparation for « day 1 »  Activities & responsibilities cover the A-to-Z of the building of a HEP experiment Outer Tracker construction and testing VELO hardware contributions Outer Tracker construction and testing VELO hardware contributions OT software VELO software contributions OT software VELO software contributions OT alignment studies OT alignment studies pattern recognition in OT & other trackers pattern recognition in OT & other trackers track reconstruction and fitting track reconstruction and fitting B-decays selection algorithms & strategies B-decays selection algorithms & strategies CP violation measurements / CP sensitivity studies CP violation measurements / CP sensitivity studies DETECTOR RECONSTRUCTION PHYSICS

19 NIKHEF Jaarvergadering, Dec /19 The ABC of (re)search in LHCb Requires: - a lot of patience - To be alert … but never given up on your nerves … - one might get stuck on the way … Searches e.g. for rare events


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