1. The X(3872) at the Tevatron Ulrich Kerzel, University of Karlsruhe for the CDF and D0 collaborations Beauty 2005

2. 24th June 2005U.Kerzel, University of Karlsruhe Beauty20052 observe at 1 fb -1 luminosity delivered early June huge inelastic cross-section: ¼ 5000 times bigger than for ) triggers are essential! events “polluted” by fragmentation tracks, underlying events ) need precise tracking and good resolution Physics at the Tevatron dedicated trigger for J/  !  +  - trigger events where m(  +  - ) around m(J/  ) ) high quality J/  events with large statistics channel J/  ! e + e - much more challenging in hadronic environment

3. 24th June 2005U.Kerzel, University of Karlsruhe Beauty20053 CDF: precise tracking: (silicon vertex detector and drift chamber) important for B physics: direct trigger for displaced vertices D0: excellent muon system and coverage large forward tracking coverage new in RunII: magnetic field ) D0 has joined the field of B physics

4. 24th June 2005U.Kerzel, University of Karlsruhe Beauty20054 Observation of X(3872) at CDF and D0 PRL 93,162002 (2004) hep-ex/0405004 PRL 93,072001 (2004) reported widths are compatible with detector resolution no signal in wrong-sign combination, i.e. X ++, X -- hep-ex/0312021 D0

5. 24th June 2005U.Kerzel, University of Karlsruhe Beauty20055 Observation of X(3872) at CDF and D0 Original observation by Belle: m(  +  - ) clusters at large values D0: demand m(  +  - ) > 0.52 GeV/c 2 as default cut CDF: separately plot m(J/   +  - ) for m(  +  - ) > 0.5 GeV/c 2 and m(  +  - ) < 0.5 GeV/c 2 ) no apparent signal for m(  +  - ) < 0.5 GeV/c 2 PRL 93,072001 (2004) hep-ex/0312021

6. 24th June 2005U.Kerzel, University of Karlsruhe Beauty20056 X(3872): central vs. forward PRL 93,162002 (2004) hep-ex/0405004 D0 D0: large muon coverage ) reconstruct X(3872) in central and forward part of the detector  2S) and X(3872) behave very similar in both rapidity ranges

7. 24th June 2005U.Kerzel, University of Karlsruhe Beauty20057 X(3872) properties ) X(3872) behaves similarly to the  (2S) compare fraction of yields w.r.t initial selection isolation: p(X) / p(X + charged tracks in cone  R = 0.5)  ,   : boost one of the pions (muons) in dipion (dimuon) rest-frame, L xy : distance (PV – decay vertex) * M/p t PRL 93,162002 (2004) hep-ex/0405004 D0

8. 24th June 2005U.Kerzel, University of Karlsruhe Beauty20058 X(3872) production fraction from B Define pseudo-proper decay time: decay PV Unbinned LogL fit (simultaneously for c  and M): Mass: signal: Gaussian BG : 2 nd order polynomial for BG Proper time: signal: exponential BG : 2 pos., 1 neg. exponential all folded with Gaussian due to resolution

9. 24th June 2005U.Kerzel, University of Karlsruhe Beauty20059 ) X(3872) behaves similarly to the  (2S) (with given uncertainties) X(3872) production fraction from B fraction from B decays:  2S): 28.3 § 1.0 (stat.) § 0.7 (syst.) % X(3872): 16.1 § 4.9 (stat.) § 1.0 (syst.)%

10. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200510 Consistency check: overlay m(J/   +  - ) spectrum with prediction from LogL ) data is described well N.B. almost no prompt signal for c  > 100  m X(3872) production fraction from B

11. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200511 The m(  +  - ) mass spectrum Distribution of m(  +  - ) constrains quantum numbers J PC shape depends on: decay of (  +  - ) sub-system: (  +  - ) in s,p,d wave (i.e. intermediate sub-resonances or not) relative angular momentum between (  +  - ) and (  +  - ) (and detector acceptance, efficiency, etc.) e.g. for decay chain: X ! J/  ,  !  +  - for broad resonances (kinematic factors vary across width) form-factor

12. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200512 The m(  +  - ) mass spectrum Challenge: Large background, rather low X(3872) yield ) sideband-subtraction difficult, instead: “slicing technique” impose bin borders in m(  +  - ) as additional cuts fit resulting (    -  +  - ) mass spectrum obtained yield shows variation with m(  +  - ) need to be careful at kinematic borders

13. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200513 The m(  +  - ) mass spectrum if (  +  - ) in S-wave state: ) shape needs to be modelled compare to multipole expansions if (  +  - ) form sub-resonance: ) shape follows Breit-Wigner e.g. decay via  0 !  +  - (no kinematics, form-factor here) m(  +  - ) favours high end of mass spectrum ) compatible with intermediate  0 !  +  - resonance also 3 S 1 multipole-expansion for charmonium possible no charmonium candidate at that mass 3 S 1 also has J PC = 1 – ) non-observation by BES (  (e + e - )B(  +  - J/  ) < 10 eV @90% C.L. ) notation: n 2s+1 L J (J PC ) hep-ph/0310261

14. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200514 X(3872) with J/  ! e + e - Reconstruction of J/  ! e + e - very difficult in complex hadronic environment dedicated J/  ! e + e - trigger use neural-network based approach to identify soft e § (p t > 2GeV/c) reject e § from conversions based on neural network approach add  at J/  vertex to accommodate Bremsstrahlung X(3872) reconstructions follows J/   +  - case (replace cut on m(  +  - ) by cut on Q = m X – m J/  – m   ) able to reconstruct X(3872) in this channel! strong radiative tail

15. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200515 What is the X(3872) ?? Charmonium ? 2 1 P 1, i.e. h 0 c (1 +- ) predicted at ¼ 3950 MeV/c 2 why is the 1 P 1 h c not seen in J/   +  - ? Belle: |cos  J/  | distribution does not fit 1 1 D 2 (2 -+ ) pos. C-parity 1 3 D 2 (2 -- ), 1 3 D 3 (3 -- ) then also decay: X !  c1 , X !  c   ) if charmonium, very unusual properties! charmed molecule? hybrid state, i.e. ? “Deuson” ? (hep-ex/0408116) notation: n 2s+1 L J (J PC )

16. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200516 DeRujula, Georgi, Glashow (1977): Charmed molecules? J/  X(3872) ?? possible formation of 4q “molecules”: decay via:

17. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200517 „Deuson“ model (Törnqvist) 00 X(3872) similar to deuteron: composed of two objects bound by  0 exchange Prediction: J PC = 1 ++ or 0 -+ (otherwise potential too weak or repulsive) small binding energy: narrow resonance, big object isospin breaking: X ! J/   0,  0 !  +  - allowed X ! J/   forbidden for any isoscalar  X ! J/   0  0 forbidden

18. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200518 Further properties by B-factories BaBar: search for charged partner X § ! J/   § expect twice the rate if X is part of iso-triplett ) no signal found Belle: 4  evidence for decay X(3872) ! J/   evidence for decay X ! J/   +     ) Swanson: 1 ++ has contribution of X ! J/  ,  !  +     search for X !  c1 , X !    ) no signal found C = +1 (hep-ph/0311229) (hep-ex/0505037) (hep-ex/0408083)

19. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200519 Conclusions & Outlook X(3872) observed at CDF and D0 with high statistical significance already many properties determined: behaves similar to  (2S): isolation, cos(  ,  ), rapidity y fraction from B decays  +  - mass distribution experimental evidence seems to point to: X(3872) has positive C parity X(3872) compatible with ‘molecular’ interpretation  +  - spectrum compatible with intermediate  0 hypothesis yet to come: determination of J PC (CDF), decay modes with photons (D0),...

20. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200520 BACKUP

21. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200521 CDF D0 Tevatron Main injector and recycler RunI: 1992 – 1996 data taking period at RunII: 2001 – 2009 major upgrades to collider and detectors The Tevatron

22. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200522 Tevatron performance Running well - both peak luminosity and integrated luminosity Currently ~15 pb -1 / week delivered 1 fb -1 delivered in beginning of June.

23. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200523 CDF: precise tracking: (silicon vertex detector and drift chamber) important for B physics: direct trigger for displaced vertices D0: excellent muon system and coverage large forward tracking coverage new in RunII: magnetic field ) D0 has joined the field of B physics

24. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200524 Physics at the Tevatron large b production rates: ) 10 3 times bigger than ! spectrum quickly falling with p t Heavy and excited states not produced at B factories: enormous inelastic cross-section: ) triggers are essential events “polluted” by fragmentation tracks, underlying events ) need precise tracking and good resolution!

25. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200525 Dedicated trigger J/  !  +  - trigger events where m(  +  - ) around m(J/  ) high quality J/  events large statistics available N.B. channel J/  ! e + e - much more challenging in complex hadronic environment! Evaluate muon chamber info on trigger level:

26. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200526 Likelihood function for measuring fraction from B define likelihood: composed of lifetime and mass functions Signal: Gaussian, m 0,  0 from full fit Background: 2 nd degree polyn. lifetime component: exponential with Gaussian resolution mass component:

27. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200527 Systematics for measuring fraction from B mass window shift window at fixed width of 130 MeV/c 2 vary width of mass window: 50-250 MeV/c 2 fit model vary parameterisations, e.g. 2 Gaussians instead of 1, etc. (negligible for X(3872)) multiple candidates (L xy dominated from J/  decay) randomly select one candidate take highest/lowest p t candidate take candidate with largest m(  +  - ) take candidate with smallest error on L xy take candidate with lowest  2 in vertex fit fit bias generate many pseudo-experiments (Toy-MC) from original fit define pulls and check for deviations from Gaussian at zero

28. 24th June 2005U.Kerzel, University of Karlsruhe Beauty200528 Systematics for m(  +  - ) measurement Yield systematics: compare yield from Gaussian with counting bin entries replace background parametrisation with polynomial (n.b. special treatment for points at kinematic boundary) vary fit window size from 200 MeV/c 2 to 150, 250 MeV/c 2 Efficiency systematics: efficiency correction determined from MC measure p t spectrum from data, vary parameters x 0 : turn-on value x low, x up : fit range