1. Beauty 2006 R. Muresan – Charm Physics @LHCb 1 Charm Physics @ LHCb Raluca Mureşan Oxford University On behalf of LHCb collaboration

2. Beauty 2006 R. Muresan – Charm Physics @LHCb 2 Outline  LHCb and its charm physics trigger  RICH calibration using D*→ D 0 (K  )  events  Charm Physics Mixing searches Direct CPV Rare decay D 0 →   Summary Unobserved phenomena

3. Beauty 2006 R. Muresan – Charm Physics @LHCb 3 For details on the LHCb detector see Lluis Garrido’s talk VELO and RICH-es are the most important detectors for charm analysis.

4. Beauty 2006 R. Muresan – Charm Physics @LHCb 4 LHCb D* trigger  L0 hardware p t of  e, h,   HLT software – confirm L0,  e, h,  alley. 2 kHz output rate 200 Hz Exclusive B specific final states 300 Hz D* → D 0 (hh)  600 Hz Di-muon J/  b → J/  X 900 Hz Single muon trigger for b data mining For details on the LHCb trigger see talk by Eduardo Rodrigues. Estimated D* → D 0 (hh)   yields, events to tape, @ 2 fb -1 from b-hadrons: D 0 → K -    50  x 10 6 ; D 0 → K - K   5  x 10 6 ; D 0 →  -    2  x 10 6 ; D 0 → K +   0.2  x 10 6. Similar number of prompt D* are expected. 10 8 potentially usable D* → D 0 (hh)  events per 2 fb -1, available for:  Charm Physics studies  RICH calibration

5. Beauty 2006 R. Muresan – Charm Physics @LHCb 5 D* → D 0 (hh)  trigger stream  RICH information not used in the trigger  unbiased sample for MC - independent offline RICH calibration.  HLT assumes K  K, KK, ,  masses in turn. K  KK  D 0 mass online/offline resolution 8.2 / 5.3 MeV GeV

6. Beauty 2006 R. Muresan – Charm Physics @LHCb 6 HLT – D* stream Loose cuts on:  hadrons p t and min IP sign,  D 0 mass and (D*-D 0 ) mass Present values favour the D * coming from b hadrons.

7. Beauty 2006 R. Muresan – Charm Physics @LHCb 7 ” Golden” kinematics easy to supress the background in order to obtain a clean sample (M D* - M D 0 )=144.5 MeV. A kaon and two pions with different momenta from each event can be used for RICH calibration. (D*-D 0 ) mass (GeV) A method to calibrate and study the performance of the RICH detector completely independent of the MC truth information using the D *+  D 0    D 0  K  decay chain RICH calibration (D * -D 0 ) mass resolution online/offline 0.61/0.45 MeV

8. Beauty 2006 R. Muresan – Charm Physics @LHCb 8 D0D0 p , K (GeV) p t , K (GeV) IP sig. , K   D 0 vertex D 0 mass (GeV) p t D 0 (GeV) >2 >0.3 >2 <16 (1.84,1.89) 1.250 D*D* IP sig. slow  Dist PV - D0 DVsig.   D * vertex p t D * (GeV) D * mass (GeV) mass ( D*- D 0 ) (GeV) >1. >6 <16 1.250 (2.000, 2.030) (0.1449, 0.1465) Offline D* events selection cuts SELECTION WITH KINEMATIC CUTS ONLY – NO RICH. Particles are attributed in turn K mass and  mass b inclusive sample, 330 s data taking; The cuts provide a very clean K and  sample (over 96% purity). 95% D 0 selected are true D 0

9. Beauty 2006 R. Muresan – Charm Physics @LHCb 9 PID performance of RICH as measured on D* sample (MC truth independent) compared with that from truth information on all tracks in b sample  e   e  K->K, p  ->K, p Kaon P (GeV) Pion P(GeV) Possible discrepancies maybe related to hidden variables (p t, multiplicity…), will be investigated with much higher MC statistics in near future.

10. Beauty 2006 R. Muresan – Charm Physics @LHCb 10 Initial focus on D 0 → h + h - decays: Charm Physics @LHCb  CP Eigenstate Lifetime Difference comparing the CP even Singly Cabibbo Suppressed (SCS) decay D 0 →K + K - (     ) with non-eigenstate Right Sign (RS) decay D 0 →K -     Oscillation studies Wrong Sign (WS) decay  D 0 →K +    Direct CP violation SCS decays D 0 →K + K - (     ) Other interesting studies are possible: investigation of D 0 → 4h modes search for D 0 →  +   many others for which the potential has not yet been estimated….

11. Beauty 2006 R. Muresan – Charm Physics @LHCb 11 mixing Indexes associated to the mass eigenstates.  av. width  sensitive to new particles in the box diagram loop  contributions from all the energy scales, sensitive to new physics  mixing through physical decay states (long range)  expected to be dominated by SM contributions tagged unambiguously at production using the slow  sign

12. Beauty 2006 R. Muresan – Charm Physics @LHCb 12 mixing SM expectations imprecise, several orders of magnitude possible, independent of discovery potential of NP precise measurement desirable. |x|,|y| are expected to be small. x enhancement ( |x| » |y| ) could signify NP. Petrov hep-ph/0311371

13. Beauty 2006 R. Muresan – Charm Physics @LHCb 13 Lifetime ratio Lifetime splitting, y CP can be measured by comparing the non-eigenstate decay D 0 → K -   to CP even decay D 0 → K + K - (     ). y and y cp differ by CP violating phase y CP (%) N (K + K - ) Data set BaBar 1.5 ± 0.8 ± 0.5 2608491 fb -1 Belle 1.2 ± 0.7 ±0.4 36480158 fb -1 CLEO- 1.2 ± 2.5 ± 1.4 24639 fb -1 FOCUS 3.4 ± 1.4 ± 0.7 10331 E791 0.8 ± 2.9 ± 1.0 3200 LHCb ~ 5x10 6 potentially useful tagged D 0 → K + K - events per 2 fb -1

14. Beauty 2006 R. Muresan – Charm Physics @LHCb 14 RICH information and D 0 → K + K - No PID With PID M KK (MeV) K+K-K+K- K+K-K+K- +K-+K- +K-+K- PID RICH information essential for eliminating the background

15. Beauty 2006 R. Muresan – Charm Physics @LHCb 15 Oscillation Search with WS K  D 0 can arrive to a WS hadronic final state (K +    via:  DCS decay  Oscilating to +CF decay 3 contributions assuming CP Data setN( K +    No CPV Belle400 fb -1 40240.72 ( -9.9, 6.8 ) BaBar57.1 fb -1 4302.0 ( -27, 22 ) CLEO9 fb -1 450.78 ( - 52, 2 ) FOCUS8.3 ( -72, 11) Strong phase difference between CF and DCS amplitudes LHCb - 0.2  x 10 6 potentially useful tagged D 0 → K +   events per 2 fb -1.

16. Beauty 2006 R. Muresan – Charm Physics @LHCb 16 WS is the more challenging channel to pick out: BR ( K +   ) = ( 1.43  0.04 ) x 10 -4 BR ( K +   ) / BR ( K -   ) = 3.76 x 10 -3. D 0, tagged using slow pion sign. Work in progress to further suppress the background peaking in m Kπ : right sign decays mistagged by combination with a random pion. RICH particle ID effectively eliminates the background peaking in Δm: double misidentification of right sign decay Preliminary Monte Carlo lifetime fitting and sensitivity studies are underway WS decay time dependent mixing - K +  

17. Beauty 2006 R. Muresan – Charm Physics @LHCb 17 D 0 production and decay vertices  D 0 lifetime measurement necessary input for mixing studies.  Need good resolution for both the production and the decay vertex D 0 lifetime  = 0.4101  0.0015 ps D 0 flight distance 60 GeV  c  mm D 0 decay vertex resolution 0.225  mm

18. Beauty 2006 R. Muresan – Charm Physics @LHCb 18 D 0 production and decay vertices Poor resolution of the D 0 production vertex = 4.270 mm to be compared to 4 mm Proper time resolution = 0.591 ps to be compared to 0.410 ps Slow pion – very low momentum → D 0 and  s almost colinear

19. Beauty 2006 R. Muresan – Charm Physics @LHCb 19 D 0 production vertex reconstruction D0D0 D*B parent x22.825017 Y19.116015 z2254270137 Vertex resolutions (  m)  Use additional tracks at production vertex 1. Prompt D* for primary vertex 2. Partially reconstruct parent B parent  Preliminary work on 2 promising, for 1 MC not yet available.  70% of D* from B’s have at least one charged sister, 45% have sister tracks which are reconstructed and pass some basic criteria Proper time resolution = 0.059ps

20. Beauty 2006 R. Muresan – Charm Physics @LHCb 20 Direct CPV in D 0 → K + K - (     ) Occurs when the absolute value of the D decay amplitude to a final state is not equal to the CP conjugate amplitude. D 0, tagged using the slow pion sign SCS decay, easy to modify its topology to get a penguin

21. Beauty 2006 R. Muresan – Charm Physics @LHCb 21 Direct CPV in D 0 → K + K - (     ) A cp (K + K - )A cp    - )N (K + K - )Data set CDF 2.0 ± 1.2 ± 0.6 1.0 ± 1.3 ± 0.616220123 pb -1 BaBar -1.3 ± 0.8 ± 0.2 0.3 ± 1.1 ± 0.22608491 fb -1 Belle- 0.2 ± 0.6 ± 0.336480158 fb -1 Cleo 0.0 ± 2.2 ± 0.8 1.9 ± 3.2 ± 0.830239 fb -1 FOCUS- 0.1 ± 2.2 ± 1.5 4.8 ± 3.9 ± 2.53330 E791- 1.0 ± 4.9 ± 1.2-4.9 ± 7.8 ± 3.0609 In SM A CP ≤ 10 -3 for SCS decays. Possible NP enhancements to 1% from, e.g., penguin diagram  LHCb ~ 5x10 6 potentially usable flavour tagged D 0 →K + K - events per 2 fb -1.  Statistical precision ~10 -3.  Normalize against initial state asymmetries through K  mode.  Baseline measurement requires no lifetime estimation → all D* from B can be used.

22. Beauty 2006 R. Muresan – Charm Physics @LHCb 22 Oscillation Search with WS K   A possible implementation of D* + →   D 0 (→4h) in the HLT is under study.  Large branching fraction B (K  ~ 2 x B (K   Important sample for complementing K +   mixing study  Sample for calibrating D decay model for 4-body Dalitz analyses in B → DK  measurement (see Yuehong Xie’s talk). LHCb large potential sample ~ 25 x 10 6 tagged K  events to tape per 2 fb -1 Rare decay D 0 →   D 0 →  strongly suppressed in SM -- 10 -18 - 10 -13.  In some SUSY models, enhancements up to 10 -6 possible.  Current best branching ratio limit BaBar: BR < 1.3 x 10 -6 (122 fb -1 ). LHCb BR(D 0 →  ) < 5 x 10 – 8

23. Beauty 2006 R. Muresan – Charm Physics @LHCb 23 Summary  The LHCb experiment has an exciting potential for charm physics studies.  A dedicated D* trigger will provide 10 8 flavour tagged D 0 →hh per 2 fb -1, giving unprecedented sensitivity in searches for D 0 mixing, CP violation and rare decays.  The same sample provides an invaluable calibration signal for LHCb performance, in particular the RICH detector.  We have only begun to tap LHCb’s potential for charm physics. Our beauty is also charming