B Physics at the LHC 1 Ulrich Uwer Heidelberg University Flavor Physics in the LHC Era Singapore, November 2010 b s Disclaimer: Due to time-constraints only LHCb

Quark Flavor Mixing 2 Within uncertainties, flavor changing data described by SM: There are several 2…3  tensions! New Physics effects only appear as corrections to leading SM terms.

“New Physics” in B-decays 3 bs u, c, t bs X Y bq q bW bq X q bY  Precision measurement of loop-suppressed effects: very high statistic and access to unexplored B s system Standard Model New Physics + + W

LHCb Search Strategies for NP 4 Explore FCNC transitions with large sensitivity to NP, especially b  s transitions (poorly constrained by current data) B s mixing phase  s Penguin and other rare decays: B s , B 0  K * , B s   but also CP violation in D decays Improve CKM elements and challenge the SM by over- constraints: Precise determination of angle  Compare tree versus loop results measurements w/ NP discovery potential Precision CKM metrology Slide by U.Egede

Outline 5 LHCb experiment Detector performance Results on flavor production Towards a measurement of  Exploring the B s sector Rare FCNC processes

B Production at LHC 6 bb bb  Cross sections predictions (PYTHIA)  s = 7, 10, 14 TeV  B ±, B 0, B s, B c,  b … (40% 40% 10% 10% from LEP)  20x larger charm production  Design L ~ 2 x cm -2 s -1 (tuned) ~ bb events / year (2 fb -1 ) 15 kHz bb-events in LHCb  inel ~ ( 0.89, 0.95, 1 )  80 mb  bb ~ ( 0.44, 0.67, 1)  ~500  b ~250  b bb Production p p b b Gluon-Gluon-Fusion: bb

Key requirements for b Physics at LHC 7 b Hadron BsBs -- K-K- ++ -- -- ++ K-K- K-K- 7 mm Excellent vertex resolution: to resolve fast B s oscillation. Background reduction:Very good mass resolution Good particle identification (K/  ) High statistics:Efficient trigger for hadronic and leptonic states t = /  c  t  40 fs

LHCb Detector 8 Muon System  /h separation Trigger Calorimeter h/e/  / separation Trigger Tracking-System RICH Detectors p/K/  Vertex Detextor

LHC Operation 9 Peak lumi ~2  cm -2 s -1 Delivered int. lumi: O(50 pb -1 ) Bunches/colliding: 368/344 Commissioning of 50 ns spacing Preparation for bunch trains End Aug Excellent performance: 3.5 TeV TeV 2010 lumi goals reached: Heavy Ion run since ~1 week Expect >1 fb -1 in 2011 March 30th

LHCb Data-taking 10 LHCb: Recorded: 37.7 pb -1 (eff.~90%) Design lumi w/ only 344*) bunches:  Large pileup, very busy events *) nominal: 2800 bunches Peak Lumi = 1.7  cm -2 s -1 Interactions / crossing

Typical Event at =2.5 11

First B candidate (single interaction) 12 First B + → J/ψ (μ + μ – ) K +

Vertex resolution 13 6 cm Both Velo halves move at every fill: nominal position of sensor: 8 mm to beam axis! Impact parameter resolution (x): Primary vertex resolution:  x  15  m  y  15  m  z  76  m Module and sensor alignment better than 5  m. Fill-to-fill variations < 5  m.

Tracking 14 LHCb Preliminary OT LHCb Preliminary TT

Mass resolution 15 m = MeV  = 14 MeV m = 5277 MeV  = 13 MeV  = 9 MeV (w/ mass constr) B +  J/  K + J/    Resolutions still slightly different from prediction: calibration and alignment ongoing. K s →  m = MeV  = 3.3 MeV

PID with RICH 16 D + →KK  D s →KK  124 nb -1 D + →K  124 nb -1 PID allows separation of topologically identical finals states

Muon Identification 17 Tracking system Muon system J/  µ probe µ tag   > 90% and mis-ID rate 10 GeV/c Mis-ID rate: K s   KK

Heavy Flavor Production 18 B + → J/ψ (μ + μ – ) K +

Inclusive J/  production 19 Inclusive J/  production:  (2.5<y<4,p T <10 GeV/c)=7.65 ± 0.19 ±  b J/  production from b: f b = (11.1 ± 0.8) %  (2.5<y<4,p T <10 GeV/c)= 0.81 ± 0.06 ± 0.13  b σ(pp  H b X; 2<η b < 6) = 84.5 ± 6.3 ± 15.6 μb polarization uncertainty Not well described by colour singlet nor by octet models. Phythia LHCb ICHEP 2010 (preliminary) LHCb ICHEP 2010

bb cross section from B  D 0 (K  )  X 20 D from B Prompt D Fake D  (pp→H b X; 2 <  < 6) = 75.3  5.3  13.0 μb ηLHCb preliminaryTheory 1Theory ± 4.0 ±11.4 μb8970 all292 ± 15 ± 43 μb Average of two measurements Theory 1: Nason, Dawson, Ellis Theory 2: Nason, Frixione, Mangano and Ridolfi LHCb assumed ~250 μb LHCb: PL B 694 (2010) 209. B  D(K  )  X LHCb ICHEP nb -1

Prospects for semi-leptonic decays 21 Fake D D from B B s  D s µX Same technique to reconstruct b  D +,D s,  c  X  b   c µX (  c  pK  ) (D s  KK  ) Allows semi-leptonic measurements: e.g. b-hadron fragmentation fractions 800 nb -1  c from B

Open Charm Production 22 Impact parameter used to separate prompt from secondary charm

Charm Cross Section 23 preliminary! e.g. D 0  K -  + Slide by Z.Yang

Spectroscopy 24 X(3872) J/        (1S)  (2S)  (3S)  (2S)

CKM Angle  25 A lot of pioneering work by B-factories Constraints from direct measurements still weak

Towards a  measurement at LHCb 26 ADS: D 0 decays suppressed (K +  - ) GLW: D 0 decays to CP state ( ,KK) GGSZ: D 0 decays to K s  (Dalitz) BB f K  D 0 K  V ub Tree Level Processes 1 fb -1 Combined sensitivity: CDF (5 fb -1 ): ~30 evts ~300 nb -1 B +  (K  )  +

B  hh 27 ~3 pb -1 B d   B s  KK B d/s  /K B d/s Loop Processes R.Fleischer Measure time dependent CP asymmetries (direct, mixing) in B d   and B s  KK. ~3 pb -1

B 0  K  28 3 pb -1 (World average: A CP ( B  K  ) =  0.012)

B s Sector – Mixing phase  s 29 SM p-value is 44% ~6500 events CDF public note bs s b  m s, , phase  s

B s  J/   30 observed yield: ~40 B s  J/  events / pb -1 B s  J/  candidate Mixture of CP even/odd final states: Angular analysis to separate CP states ~17 pb -1 ~670 evts

Flavor Tagging 31 Expected Tagging performance: Uncalibrated tagging algorithms applied to B 0  D*  (D 0   )  + evts : ~60% of expected performance. Calibration & tuning ongoing.  m= 0.53 ± 0.08  s pb -1 opposite side same side (simulation) tagging power  stat. weight  D 2 = 6.2% (MC)

Control Channels 32 B +  J/  K + B 0  J/  K* 0 Tagging calibration (opposite side) Kinematically similar to B s  J/  Angular acceptance checks: Polarization amplitudes Check of tagging performance ~17 pb -1

Expected Sensitivity 33 35k selected evts / 1 fb -1 (based on measured  bb ) = 38 fs Tagging:  D 2 =6.2% S/B as in simulation MC 2010

Semi-leptonic asymmetries a sl 34 Evidence of anomalous CP-violation in mixing of neutral B mesons by D0. Inclusive method at LHCb difficult due to the production asymmetry in pp collisions (~10 -2 ) and detection asymmetries. A. Lenz, U. Nierste, 2007 SM: ~10 -4  X X  + X B0B0 B0B0 B0B0 B0B0 CP PRD 82, (2010)

Prospects at LHCb 35 Time dependent asymmetry difference of semi-leptonic B decays: B s + →D s (KK  )μ and B 0 →D + (KK  )μ : (cancels detection asymmetries and allows simultaneous fit of prod. asymmetry) LHCb Method: a sl (B s ) - a sl (B d ) ~0.6 pb -1 stat. only

Penguin and very rare FCNC decays 36 b  s  penguins B d  K*  Very rare FCNC proc. B d,s  

B 0  K*  37 Standard Model Corresponding Wilson coefficients C i describe short-range physics. New Physics in Wilson coefficients C i = C i SM + C i NP or new operators. Effective Theory Operator Product Expansion

New Physics Sensitivity 38 Observables:  l,  K, , m 2  A FB (q 2 ) ~ - Re  C 10 eff * [ C 7 eff +  (q 2 ) C 9 eff ]   forward-backward asymmetry: q2q2 High sensitivity of angular observables CDF: 100 evts CDF Public note BELLE: 250 evts PRL 103 (2009) BABAR:100 evts PRD 79 (2009) A FB (q 2 ) for B 0  K*  ~450 evts

Prospects 39 LHCb expectation for 1 fb -1 ~1400 events w/ B/S~ events for 100 pb -1 B 0  J/  K* for selection efficiency and background studies: Just 0.1 fb -1 will give equivalent error to B-factory measurement.

Very Rare Decays - B d,s  Large NP contributions possible SM: BR(B s  μ + μ - )= (3.6±0.3)x10 -9 BR(B d  μ + μ - )= (1.1±0.1)x A. Buras (2009) CDF Public note 9892 arXiv:

LHCb Prospects for B d  41 LHCb strategy: 3 discriminants Invariant mass Geometrical likelihood Muon likelihood

Conclusion & Outlook 42 LHC and the LHC(b) experiment(s) perform amazingly well. LHCb has recorded ~40 pb -1 of high-quality data in 2010 First competitive B-physics results for Moriond 2011: B s mixing, mixing phase  s, limit on B s , D results For 2011 expect 1 fb -1 (minimum) of data:  results for all LHCb key measurements. Flavor Physics at the LHC has started

Backup 43

Semileptonic Asymmetries 44 S. Hansmann

Semileptonic Asymmetries 45 S. Hansmann

Production ratio D + / D s + 46  (D + ) /  (D s + ) = 2.32  0.27  0.26 Consistent with PDG: f(c  D + ) / f(c  D s + ) = 3.08  0.70 preliminary!

Charm – Mixing and CPV 47 D*  D(K  )  s 124 nb -1 ~17k evts

Comparison with “high-p t ” Detectors 48 ATLAS/CMS: |  | < 2.5 LHCb: 2<  < 5 ATLAS/CMS: Optimized for high-p t signatures very restricted particle ID B-physics limited to muon triggers, large p t (>4…6 GeV) Small bandwidth by T.Skwarnicki

Mass resolution 49 ATLASCMSLHCb σ ( J/  ) 70 MeV47 MeV14 MeV σ (  ) 170 MeV100 MeV47 MeV

Impact parameter resolution σ (IP) 60 µm50 µm25 µm

B s  51 Expected results (assuming σ(pp → bbX) = 500 –Uncertainty coming from limited amount of MC –B → J/  K is used for normalization to translate the signal cross section to a BR N sigN bkg90% CL ATLAS (10 fb -1 ) CMS (1 fb -1 )2.46.5< with 10 – 20 fb -1 SM prediction region 3σ evidence after σ observation after 1 34 with 10 – 20 fb -1 SM prediction region 3σ evidence after σ observation after * * Scaling quoted result by ratio of LHCb measured x-sec at √s = 7 TeV to 14 TeV value assumed in MC study. CMS Prel. N sig = 48 σ M = 32 MeV/c 2 MC 280 nb -1 P.Perrret, HQL 2010

J/  from B 52