nikhef jaarvergadering, 21-22 dec. 2005 1/19 physics studies and track reconstruction in lhcb at...

NIKHEF Jaarvergadering, 21-22 Dec. 2005 1/19

Physics Studies and Track ReconstructionPhysics Studies and Track Reconstructionin LHCb at NIKHEFin LHCb at NIKHEF

E. Rodrigues, on behalf of the NIKHEF–LHCb groupE. Rodrigues, on behalf of the NIKHEF–LHCb group

CP violation / B physicsCP violation / B physics

- general introduction

LHCb experimentLHCb experiment

- basics

- LHCb group @ NIKHEF

Physics (preparation) studiesPhysics (preparation) studies

- NIKHEF contributions

Tracking / ReconstructionTracking / Reconstruction

- group’s involvement

NIKHEF Jaarvergadering 2005NIKHEF Jaarvergadering 2005


CP Violation in the B Sector

b

s

d

VVV

VVV

VVV

b

s

d

tbtstd

cbcscd

ubusud

'

'

'

Origin of CP-Violation in the SM: CKM Matrix

complex and unitary• 4 parameters:

• 3 Euler angles• 1 Phase

CP ViolationCP Violation

1Re

0

Im

Re

/0 JBs

,21, 2

cb

ub

V

V

0

Im

Re

00 KccB

,.....,,0 B

2 KDB ss

Unitarity Triangle(s)Unitarity Triangle(s)

VVVV++ = V = V++V = IV = I


(side view)

pp collision

Acceptance

10 mrad

250/300 mrad

LHCb Detector

Single Arm Forward Spectrometer

« Tracking » detectors« Tracking » detectors


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


NIKHEF – LHCb Group (part of)

Practicing Team buildingPracticing Team buildingBarcelona 9/’05

After Jeroen’s promotie 10/’05


Master & PhD Theses in 2005

• Jan Amoraal

• Sander Klous

• Besma M’charek•

• Jeroen van Tilburg

Jeroen van Tilburg

… after the promotie in Oct. ’05 !Thesis “Track simulation and reconstruction in LHCb”Thesis “Track simulation and reconstruction in LHCb”

ThesisThesis “LHCb: vertex detector and read out chip, “LHCb: vertex detector and read out chip,computing challenge and Bcomputing challenge and Bss -> J/ -> J/ ””

2005

PhD

PhD Post-doc … off to Zűrich in ‘06

Jan June Dec

Master

PhD Post-doc @ ATLAS

Next PhD’er on the pipeline: Bart Hommels ...Next PhD’er on the pipeline: Bart Hommels ...

… … has already a job in Cambridge!has already a job in Cambridge!

PhDMaster


Physics Studies

B0sDs B0

sJ/(μ+μ-) K +,* B0sμ+ μ-

ms

Marcel Merk

Gerhard Raven

Jeroen van Tilburg

B0sDs K

Commissioning / lifetimesCommissioning / lifetimes

Gerhard Raven

Peter Vankov

B0sJ/(μ+μ-)

Rare eventRare event

New physicsNew physics

N. A. … yet …

BXs 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 physicsNew physics

Marko Zupan

Year 1

> Year 1> Year 1


s from B0s Ds Decays

Marcel MerkGerhard RavenJeroen van Tilburg

MC truthReconstructed

If ms = 25 ps -1

Bs mixing can be clearly observed in Bs Ds

with one year of data taking

Once oscillation observed, ms can be measured

with very high statistical precision ms)=0.01ps-

1

ms 20ps-1 25ps-1 30ps-1

sensitivity in one year:

( assuming 55 < <105 )

LHCb in pole-position for LHCb in pole-position for mmss::

- Excellent vertex resol. and- Excellent vertex resol. and

proper time resol.proper time resol.

mm


from B0s Ds K Decays

Thomas BauerBesma M’charekMarcel MerkJeroen van Tilburg

( taking ms = 20 ps-1 )

@ NIKHEF:@ NIKHEF:

- Responsible for the selection strategy- Responsible for the selection strategy

- Drives the sensitivity studies- Drives the sensitivity studies

N.B.: we were amongst the first to use the Grid for these sensitivity studies!

trec

5 years data:Bs→ Ds

-

Bs→ Ds-K+

ms = 20 ps-1)


B0s J/+-Decays

Jan AmoralSander KlousGerhard Raven

• ““golden decay”, theoretically cleangolden decay”, theoretically clean

• Measurement of Measurement of angle and angle and ss

- very small in SM: sin 2- very small in SM: sin 2 = 0.04 = 0.04

- any large asymmetry means new physics- any large asymmetry means new physics

• If If ssss is ~0.1, can do a 5 is ~0.1, can do a 5 discovery in one year, discovery in one year,almost independent of specific parametersalmost independent of specific parameters

• Time for 5Time for 5 discovery of new physics in B discovery of new physics in Bss mixing mixingdepends on the size of the new physics contribution…depends on the size of the new physics contribution…

BsJ/ψφ (Bs tagged)

Proper time τ (ps)

Such an observed distribution would mean new physics …Such an observed distribution would mean new physics …

LHCb annual yield ~ 120k events!LHCb annual yield ~ 120k events!


Inclusive B Xs+-Decays

Marko ZupanGoal:Goal: Study of inclusive b -> s Study of inclusive b -> s decaysdecays

Theoretical interest:Theoretical interest: Rather sensitive to new physics via loopsRather sensitive to new physics via loops

(e.g. SM vs SUSY)(e.g. SM vs SUSY)

Experimental aspects:Experimental aspects: BR ~ 10BR ~ 10-6-6 … too low for B-factories … … too low for B-factories … In practice XIn practice Xss is made “as inclusive as possible” is made “as inclusive as possible” Annual yield ~ 9000 events!Annual yield ~ 9000 events!

Forward-backward asymmetry Forward-backward asymmetry AAFBFB(s)(s)

s=M(+)2 [GeV2]

SM diagramsSM diagrams


Tracking / Reconstruction

NIKHEF“software” group

Group’s involvement in …Group’s involvement in …

OT event model & alignment studies:OT event model & alignment studies: NIKHEF responsibilityNIKHEF responsibility

Tracking event model :Tracking event model : NIKHEF responsibilityNIKHEF responsibility Driving forceDriving force

Pattern recognition:Pattern recognition: Many contributions: seeding, fast (online) seeding, matchingMany contributions: seeding, fast (online) seeding, matching

Track Fitting :Track Fitting : NIKHEF responsibilityNIKHEF responsibility

Magnetic field map:Magnetic field map: Participation in B-field map measurementsParticipation in B-field map measurements Responsible for including the real field map in software, for physicsResponsible for including the real field map in software, for physics


Tracking Strategy in LHCb

A typical event:A typical event: 26 long 26 long tracks tracks best quality for physics: good P & IP resolution best quality for physics: good P & IP resolution 11 upstream tracks 11 upstream tracks lower p, worse p resol., but useful in the RICH1 pattern recognition lower p, worse p resol., but useful in the RICH1 pattern recognition 4 downtream tracks 4 downtream tracks improves K improves Kss finding efficiency (good p resolution) finding efficiency (good p resolution) 5 seed/T tracks 5 seed/T tracks used in the RICH2 pattern recognition used in the RICH2 pattern recognition 26 VELO tracks 26 VELO tracks used in primary vertex reconstruction: good IP resolution used in primary vertex reconstruction: good IP resolution

|B| (T)

Z (cm)

B-field measured to ~ 0.03% precision!B-field measured to ~ 0.03% precision!


Marko Zupan

- L1 VELO tracks + L1 muon seeds +- L1 VELO tracks + L1 muon seeds +

binary tracker hit datebinary tracker hit date

- Moderate efficiency ~30% obtained but- Moderate efficiency ~30% obtained but

very high rate reduction ~400!very high rate reduction ~400!

- Peak resol. < 100 MeV- Peak resol. < 100 MeV

- Promissing trigger for calibration data …- Promissing trigger for calibration data …

under further study …under further study …

L1L1 tracking tracking

Online Pattern Recognition

L0L0 tracking tracking

Bart HommelsNiels Tuning

J/mass peak @ the L1 trigger

Pile-up veto strategies / algorithm (and hardware) is NIKHEF responsibilityPile-up veto strategies / algorithm (and hardware) is NIKHEF responsibility Performance & robustness studies being finalizedPerformance & robustness studies being finalized Pile-up veto detector can also be used for a luminosity measurementPile-up veto detector can also be used for a luminosity measurement


Offline Pattern Recognition

Henk Jan BultenBart HommelsJeroen van TilburgGabriel Ybeles Smit

OfflineOffline tracking in numbers: tracking in numbers: ~ 95% B-decay products found~ 95% B-decay products found Ghost rate ~ 3%Ghost rate ~ 3%

NIKHEF contributions:NIKHEF contributions:

- Responsible for seeding PR in the T stations- Responsible for seeding PR in the T stations

- getting it ready for a realistic detector- getting it ready for a realistic detector

- VELO-seed matching PR maintained- VELO-seed matching PR maintained

VELO

TTTT

T2T2 T3T3T1T1Efficiency for long tracksEfficiency for long tracks

ε ~ 95% (p>5 GeV)


Track Fit à la Kalman

Eduardo RodriguesJeroen van Tilburg

Benefits of the Kalman filter technique:Benefits of the Kalman filter technique: Mathematically equivalent to least Mathematically equivalent to least 22 method method Adds measurements recursivelyAdds measurements recursively

starting from a initial track estimatestarting from a initial track estimate Reconstructs tracks including multiple scattering and energy lossesReconstructs tracks including multiple scattering and energy losses

Ongoing work:Ongoing work:

- Adapting fit for a realistic detector …- Adapting fit for a realistic detector …

Note: Fitted with single Gaussian in each bin

Reconstructed tracks

Ideal tracks

prediction stepfilter step

Momentum resolution ~ 0.35%Momentum resolution ~ 0.35%


Tracking in a Realistic Detector

Edwin BosMarcel MerkGerhard RavenEduardo RodriguesJeroen van Tilburg

Warped TT sensors

“banana-shaped” Outer Tracker modules

Needs:Needs: Tracking in a realistic environment:Tracking in a realistic environment:

• move away from ideal MC to real worldmove away from ideal MC to real world• tilted and/or deformed detectorstilted and/or deformed detectors• deal with misalignmentsdeal with misalignments

Idea:Idea: Use the concept of “trajectories” developed in BaBarUse the concept of “trajectories” developed in BaBar

• a track’s trajectory can be approximated locallya track’s trajectory can be approximated locally as a parabolaas a parabola• one could also parameterize locally a detectorone 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 isparabola, whatever the shape of the whole is

Track fit is then “reduced” to a à la Kalman Track fit is then “reduced” to a à la Kalman minimization of distances between local parabolic minimization of distances between local parabolic trajectories approximations!trajectories approximations!

track fit blind to details of detector shapes and track fit blind to details of detector shapes and misalignementsmisalignements


In short …

Excellent group spiritExcellent group spirit

Lots of interesting, exciting and fun workLots of interesting, exciting and fun work

Heavy involvement in a variety of Heavy involvement in a variety of complementarycomplementary aspects of LHCb preparation for aspects of LHCb preparation for « physics @ day 1 »« physics @ day 1 »

Activities & responsibilities cover the A-to-Z of the Activities & responsibilities cover the A-to-Z of the building of a HEP experimentbuilding of a HEP experiment

Outer Tracker construction and testing VELO hardware contributionsOuter Tracker construction and testing VELO hardware contributions

OT software VELO software contributionsOT software VELO software contributions

OT alignment studiesOT alignment studies

pattern recognition in OT & other trackerspattern recognition in OT & other trackers

track reconstruction and fittingtrack reconstruction and fitting

B-decays selection algorithms & strategiesB-decays selection algorithms & strategies

CP violation measurements / CP sensitivity studiesCP violation measurements / CP sensitivity studies

DETECTORDETECTOR

RECONSTRUCTIONRECONSTRUCTION

PHYSICSPHYSICS


The ABC of (re)search in LHCb

Requires:Requires:- a lot of patience- a lot of patience - To be alert- To be alert

… … but never given upbut never given upon your nerves …on your nerves …

- one might get stuck on the way - one might get stuck on the way ……

Searches e.g. for rare events

nikhef jaarvergadering, 21-22 dec. 2005 1/19 physics studies and track reconstruction in lhcb at...

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