At LHCb William Reece on behalf of the LHCb collaboration Imperial College London Beauty ‘09, Heidelberg, 7 th -11 th September 2009

at LHCb William Reece on behalf of the LHCb collaboration Imperial College London Beauty 09, Heidelberg, 7 th -11 th September 2009

A Possible (Near) Future William Reece - Imperial College LondonPage 2 0.1fb -1 ~ 320 events 2fb -1 is one nominal year of running SM Generator Events - Signal only

A Possible (Near) Future William Reece - Imperial College LondonPage 3 0.5fb -1 ~ 1600 events 2fb -1 is one nominal year of running SM Generator Events - Signal only

A Possible (Near) Future William Reece - Imperial College LondonPage 4 1fb -1 ~ 3200 events 2fb -1 is one nominal year of running SM Generator Events - Signal only

A Possible (Near) Future Page 5 2fb -1 ~ 6400 events 2fb -1 is one nominal year of running SM Generator Events - Signal only Generated with FBMSSM [Altmannshofer, Ball, Bharucha, Buras, Straub, Wick, (JHEP 0901:019,2009)] (LHCb would observe with ~0.1fb -1 in this scenario) FBMSSM SM Line from JHEP 0811:032,2008 NLO Model Independent MC Model: A. Bharucha & WR, Preliminary

First observed at Belle Particles in Loop Both neutral and charged NP (replace W , Z 0 / , u/c/t) Sensitive to NP in loops Use OPE: Model independent Dominated by C 7, C 9, C 10 in SM Enhance other operators with NP Measure Wilson coefficients Discover or limit NP in loop William Reece - Imperial College LondonPage 6 O7O7 O 9,10 See G. Hillers talk for more info

William Reece - Imperial College LondonPage 7 Decay Kinematics Decay described in terms of 3 Angles and 1 Invariant Mass l, K, and q 2, the invariant mass squared of pair

What to Measure? Angular observables Small theory uncertainties Experimentally accessible E.g. forward-backward asymmetry of pair (A FB ) Sensitive to interference between Plausible NP models Large deviations Zero-crossing point (q 2 0 ) Accessible with small integrated luminosities (~0.5fb -1 ) Form factors cancel at leading order William Reece - Imperial College LondonPage 8 Altmannshofer et al, JHEP 0901:019,2009 ~ 4/3 A FB (CP Ave.)

Current Status William Reece - Imperial College London BaBar (2008) ~100 events, Belle (2009) ~ 250 events ~0.1fb -1 data set will give LHCb the same statistics as currently available LHCb (2fb -1 ) ~ 6.4k events Observables only reliably calculable in q 2 region 1-6 GeV 2 /c 4 Up to LHCb to see what is really going on! (SM + Errors from [JHEP 0811:032,2008]) Page 9 Belle 2009 BaBar 2008 Belle (2009) 0904.0770 BaBar (2008) PR D79:031102 Change in sign convention q 2 (GeV 2 /c 4 )

LHC Challenging Environment LHCb Optimized for B-physics B d vertex res. ~110 m Track momentum ~0.5% B d mass res. ~ 14 MeV Good ID performance key 93% efficient with 1% mis-ID /K separation from RICHs Important for selection Selecting Signal at LHCb William Reece - Imperial College LondonPage 10

Toy MC Acceptance Effects Geometry & reconstruction biases angular distribution Few events in l tails Large asymmetry Tend to loose these events at low q 2 as one is soft p T cuts make effect worse must avoid Can bias A FB distribution Must be careful in selections (10%) on acceptance fn. ~5% effect on A FB Page 11 Effect of geometry & reconstruction on signal efficiency (full MC)

Toy MC Acceptance Effects Geometry & reconstruction biases angular distribution Few events in l tails Large asymmetry Tend to loose these events at low q 2 as one is soft p T cuts make effect worse must avoid Can bias A FB distribution Must be careful in selections (10%) on acceptance fn. ~5% effect on A FB Page 12 Effect of geometry & reconstruction on signal efficiency (full MC) Effect of a 300 MeV p T cut on signal efficiency (toy MC)

Offline Selection Investigated Fisher Improves selection efficiency and signal/background over cut-based Important variables: B d : flight & IP significance, p T K & : PID, IP significance 2fb -1 yield estimate Sig. 64001600, Bg. 1590320 S/(S+B) = 7111 Total : 1.080.01 % in 4 William Reece - Imperial College LondonPage 13 Tail of Fisher discriminant Cut at 0.38 S/(S+B) = 7111 Signal Background

Trigger Selection Offline Selection Acceptance Effects II Trigger & offline selection No further significant biases introduced Detector effects dominant Will be source of systematic uncertainty Can use MC Correct with data? Use B d J/( ) K* as control channel Collect with same trigger & selection William Reece - Imperial College LondonPage 14 B d K* B d J/ K* Must understand the effect due to different kinematics

q 2 (GeV 2 /c 4 ) forward Counting Experiments for A FB Can extract A FB by counting forward and backward Relatively simple Small integrated luminosity Allows zero-crossing extraction (q 2 0 ) ~ 0.8 GeV 2 /c 4 (0.5 fb -1 ); 0.5 GeV 2 /c 4 (2 fb -1 ) Also unbinned counting in q 2 with polynomials (q 2 0 ) A FB gradient Binned in q 2 Simple Counting q 2 (GeV 2 /c 4 ) backward Fit in mass peak & sidebands for background Sig: 3 rd order BG: 1 st order CERN-LHCb-2009-03 Combine to get corrected A FB. (q 2 0 ) ~ 0.5 for 2 fb -1 q 2 (GeV 2 /c 4 ) Page 15 q2q2

Allowed Regions Assumes all NP in C 7 and C 7 , and all real SM A FB most sensitive to C 7 & C 9 Must consider other observables Combine for full discovery power Interested in C 7 , C 9 , C 10 NP phases also possible Must look at CP asymmetries too Focus on C 7 here Right-handed partner of C 7 Helicity suppressed by m s /m b in the SM Current constraints driven by Other Observables William Reece - Imperial College LondonPage 16 JHEP 0807:106, 2008.

MSSM: C 7 0 SM JHEP 0811:032,2008 Beyond A FB (C 7 ) Access C 7 in A T (2) Theoretically clean: FF cancel at LO like A FB zero Access in angle oscillation Kruger & Matias, Phys.Rev.D71:094009, 2005. CERN-LHCb-2008-057, CERN-LHCb-PUB-2009-08 Study in projection fits or 3D fit to (low q 2 ) Similar C 7 sensitivity to Also get via S 5 observable Has a zero-crossing point in SM Altmannshofer et al, JHEP 0901:019,2009 Component of angular distribution Page 17

Counting Expt. for S 5 Good for early data Zero-crossing Steeper gradient than A FB in SM smaller uncertainty Must understand acceptance Complicated (two angles) Sensitive to C 7, C 7 , C 9, C 10 Complementary to A FB William Reece - Imperial College LondonPage 18 A. Bharucha, WR, preliminary Toy MC 2fb -1 SM JHEP 0901:019,2009 MFV MSSM

Tagged CP Asymmetries Reconstruct mode self tagging Search for direct CP violation phase in Wilson coefficients William Reece - Imperial College LondonPage 19 GMSSM I : Arg(C 7 ) -3/4 Large phases allowed Experimental precision good enough to measure Extract CP asymmetries from angular distribution Best precision using full angular analysis LHCb 10fb -1 SM Egede, Hurth, Matias, Ramon, WR Preliminary 1, 2

Full Angular Analysis Perform fit for spin amplitudes Assume polynomial q 2 variation Calculate any observable from amplitudes New observables A T (3) A T (4) optimized for C 7 sensitivity 10fb -1 sensitivities for SUSY input JHEP 0704 (2007) 058 model b Allowed by experimental constraints MC Fits converge with 2fb -1 3D acceptance a challenge Hope to extract from data William Reece - Imperial College LondonPage 20 CERN-LHCb-2008-041 JHEP 0811:032,2008 SM Theory Distribution Toy fits to SUSY model b (C 7 != 0) 1, 2 LHCb 10fb -1

Summary Excellent prospects for discovery of NP Hints from B-factories? Expect 6.4k signal events per year (2fb -1 ) Whole q 2 range 0.1fb -1 gives ~350 events Same as all current experiments combined Exciting Physics program Many observables to study CP conserving and violating Real discriminating power for NP William Reece - Imperial College LondonPage 21

BACK UP SLIDES William Reece - Imperial College LondonPage 22

Finding New Physics in C 7 William Reece - Imperial College LondonPage 23 A T (3) Theory + LHCb 10fb -1 A T (4) Theory + LHCb 10fb -1 Egede, Hurth, Matias, Ramon, WR. Preliminary (0.083,-0.21) C 7 = C 7 SM + C 7 NP SM After 10fb -1 Analysis?

Trigger Strategy William Reece - Imperial College LondonPage 24 Hardware Software Current L0 Trigger selects ~93% of offline events Three lines: Single : p T > 1.3 GeV (90%) Di-: p T > 1.5 GeV, p T > 100 MeV (63%) Hadron: Calo E T > 3.5 GeV (20%) (Di-) p T cuts bias A FB shape Avoid further cuts in HLT and offline selection HLT: Lifetime biased (IP, Vertex displacement) Selects ~90% of offline and L0 events

Cut Based Selection Updated detector simulation Inclusive sample used for background Hard cuts: lifetime biased quantities Compensates for lack of p T cuts Optimized to be robust Still get signal in early data 2fb -1 yield Sig. 43001100, Bg. 200140 S/(S+B) = 649 William Reece - Imperial College LondonPage 25

Outside the Theoretically Clean Region B Vector form factors large source of theoretical uncertainty Dominated by low energy effects 7 independent functions of q 2 V, T 1,2,3, A 0,1,2 Use SCET to reduce 7 2 at Leading Order Only valid in range 1-6 GeV 2 /c 4 Can not handle resonances or low q 2 region Observables where 2 remaining FF cancel A FB zero-crossing point and A T (2,3,4) Uncertainties outside this region much greater See Beneke et al, Nucl. Phys. B612 (2001) 26-58 William Reece - Imperial College LondonPage 26

Dominated by genuine from B d Little mis-ID in MC dominant contribution Symmetric in l, scales A FB observed Increases error on zero crossing significant Asymmetric in l, affects A FB Non-resonant thought to be small Limits set from Will measure in data Background at LHCb William Reece - Imperial College LondonPage 27 No. of Events background from: b + c, c background from: b No. of Events l / rad

Drell-Yan Backgrounds Not significant background at LHCb Full simulation study: decays dominant source of in mass range Drell-Yan production much lower Reconstruction Efficiency: 1.Fake signal need a K* from elsewhere 2.Wrongly associate this with vertex 3.Mis-ID rate should be very low William Reece - Imperial College LondonPage 28

SM input + errors Angular projections of l, , K distributions Perform simultaneous fit in q 2 bins Improve precision on A FB by ~2 Measure new observable A T (2) with poor resolution in 1-6 GeV 2 /c 4 region due to (1-F L ) suppression F L (1 q 2 6) 0.86 in SM Massless Projection Fits [CERN-LHCb-2007-057] [Lunghi et al, JHEP 0704 (2007) 058] LHCb 2fb -1 BaBar Belle 08 William Reece - Imperial College LondonPage 29

Projection Fit Resolutions Results from CERN-LHCb-2007-057 William Reece - Imperial College LondonPage 30

F L small in SM for q 2 1GeV 2 /c 4 Production rate high at low q 2 (30-1000 MeV) Massless approx still valid. Dominated by C 7 in SM Yield ~200 per 2fb -1 : Sig./Bg. ~ 1 A T (2) from 2D or 3D q 2 binned fit Assume acceptance factorizes and 1 even. Check with full MC F old over and l 2fb -1 sensitivity: (A T (2) ) ~0.2 Comparable to for A R /A L William Reece - Imperial College LondonPage 31 LHCb full MC Fast Sim.

Proposed cuts in offline selection William Reece - Imperial College LondonPage 32

Angular Distribution William Reece - Imperial College LondonPage 33

Physics Sensitivity to K* Spin Amplitudes William Reece - Imperial College LondonPage 34

Observables William Reece - Imperial College LondonPage 35

Experimental Constraints for C 7 Plot William Reece - Imperial College LondonPage 36 Bobeth et al, JHEP 0807:106, 2008.

Documents

At LHCb William Reece on behalf of the LHCb collaboration Imperial College London Beauty ‘09, Heidelberg, 7 th -11 th September 2009