Andrei Nomerotski (Oxford), 29 July 2006

1. Andrei Nomerotski (Oxford), 29 July 2006 B Spectroscopy at DZero Outline • Bs hadrons at Tevatron • DZero • Excited B mesons • First Evidence of Bs* • First observation of BsDs(2536)mnX • Lambda Baryons

2. Tevatron • Excellent performance in 2005-2006 : 1.2 fb-1 on tape per experiment • Successful shutdown ended in June – detectors upgraded • Expect 4-8 fb-1 by the end of Run2 in 2009 • Results presented here use 1 fb-1

3. b-Quark • Produced strongly at Tevatron : crossection x1000 wrt B-factories …but large background • Long lifetime and heaviness  significant theoretically and experimentally Tevatron has access to B hadron species inaccessible in other colliders (modulo recent Y(5S) dataset at Belle)

4. SMT H-disks SMT F-disks SMT barrels DZero Detector • Spectrometer : Fiber and Silicon Trackers in 2 T Solenoid • Energy Flow : Fine segmentation liquid Ar Calorimeter and Preshower • Muons : 3 layer system & absorber in Toroidal field • Hermetic : Excellent coverage of Tracking, Calorimeter and Muon Systems

5. DZero Detector in Collision Hall

6. Spectroscopy of Excited Mesons One Heavy Quark Light quark(s), gluons, “brown muck” In Heavy Quark Limit, each energy level has pair of degenerate states given by: L=1 states, also known as B** L=0

7. Excited B Spectroscopy

8. Excited B Analysis • Search for narrow states decaying to B+(*)p • B1 B*+p-; B*+  B+g • B2*  B*+p-; B*+  B+g • B2*  B+p- • Reconstruct B+ J/y K+ with J/y  mm BJ selection • For each B hadron an additional track with • PT> 0.75 GeV • Correct charge correlation (B+p- or B-p+) • Since BJ decays immediately after production, track was required to originate from primary vertex. ~16K B+ J/y K+ Primary vertex

9. Excited B Results • Form mass difference DM=M(Bp)-M(B) • 3 peak structure • 1 peak direct decay B2*  B+p • B2*  B+*p with B+*  B+g (g has energy of 45.78 ± 0.35 MeV) since g is not reconstructed, we expect a peak separated from direct peak by g energy • B1 B+*p (mass peak shifted down by photon energy) (Note B1  Bp is forbidden by angular momentum and parity conservation) Results: M(B1)=5720.8 ± 2.5(stat) ± 5.3 (sys) MeV M(B2*)-M(B1)= 25.2 ± 3.0(stat) ± 1.1 (sys) MeV G1=G2= 6.6 ± 5.3(stat) ± 4.2 (sys) MeV First measurement of production rate, world’s best mass measurement.

10. Excited B Results 0.513 ± 0.092(stat) ± 0.115(sys) 0.545 ± 0.64(stat) ± 0.071 (sys) 0.165 ± 0.024 (stat) ± 0.028 (sys)

11. Bs2: Excited Meson • States similar to B1 and B2* should exist in system, i.e. there should be Bs1 and Bs2* mesons; • Almost no information exist on these objects: few claims of indirect observation at LEP: OPAL and DELPHI;

12. Previous Observations • Inclusive reconstruction of B and the correlation of “B” and K charges; • Did not provide consistent interpretation: OPAL – fitted both with Bs1 and Bs2*, DELPHI claims only Bs2* and claims that Bs1 missing;

13. Bs**: possible decays • Like for normal B**, there should be narrow Bs1 and Bs2* states; • Due to the isospin conservation, possible decays are: • Bs1B* K; • Bs2*B K, Bs2B* K;

14. Similar to B**, quark model predicts two wide (B*s0 and B*s1) and two narrow (Bs1 and B*s2) bound P states in bs system Due to Isospin conservation, the decay to Bsp highly suppressed Search for excited states decaying to B+K- Similar to B** search For each B hadron an additional track PT > 0.6 GeV Charge opposite to charge of B+ Track was required to originate from primary vertex Kaon mass assigned to track Search for B*s2 Primary vertex

15. Results 1 fb-1 D0 RunII preliminary Mass difference DM=M(B+K-)-M(B+)-M(K-) Significance of signal > 5. First Direct observation of B*s2 Wrong sign charge correlations shows no evidence of a peak MC B** decaying to B(*) p but reconstructed as B+K- show no evidence of a peak. • M(B*s2) = 5839.1 ± 1.3 MeV • Note: Bs1 can only decay to B*+K-, the theory predicts the same mass splitting: M(B2*)-M(B1)= 25.2 ± 3.2 MeV, then Bs1 decaying to B*+K- is forbidden since • M(Bs1) < M(B*+) +M(K-). Decay of B*s2 B*+ K- would produce a signal at ~ 20 MeV, however due to such a small mass difference and the additional suppression factor due to the orbital angular momentum L=2 result in a strong suppression of this decay,

16. Where is Bs1? • Suppose that M(Bs2) – M(Bs1)  M(B2) – M(B1), • Take M(B2) – M(B1) = 26 MeV from our B** study, • We conclude that decay B1sB* K should be prohibited, or at least strongly suppressed, because: M(Bs1)M(Bs2) – 26 MeV= 5813 MeV < M(B*)+M(K). • It means that the possible decay of Bs1 is EM decay: Bs1Bs(0)

17. D** and Ds** Mesons • Similarly to B** and Bs** mesons there exist D** and Ds** mesons • They are obviously better studies but there some room for improvement, especially studying B/Bs decay chains containing D** or Ds** mesons • Spectroscopy of D** is similar to that of B**

18. Reconstruction of Ds(2536) Meson We will look for narrow (L=1,jq=3/2,JP=1+) in Data: 1 fb-1 Muon plus 5-Track final state 82130 D* candidates In 0.142-0.149GeV mass difference window

19. Reconstruction of Ds(2536) Meson D±s1(2536) signal Gaussian for the signal plus an exponential with a threshold cutoff at M(D*) +M(KS) 0 • 43.8±8.3 D±s1(2536) candidates • 5.3 σ significance • 2535.7±0.5(stat)±0.6(sys) MeV/c2 • 2535.34±0.31 PDG Towards investigation of D±s1(2536) properties — there are no experimental measurements of Br(BS→DS**)

20. Br measurement • Product Br • Assuming • To be compared to theoretical predictions for

21. Lb • Lightest b baryon (udb) • Rich physics program in the Λb • Spin role in heavy hyperons (polarization) • CP violation • Exotics : T violation or other new physics in • Testing HQE theory in b baryons (lifetime)

22. Status as a few years ago. (*) (*) Includes D0 and CDF Run II measurements Lifetime A lot of theoretical work

23. Measurement of Lb lifetime

24. Conclusion • Tevatron ramps up production of excited results including excited B and D mesons • First observation of B1 and B2 as two separate peaks, measurement of masses • First direct observation of Bs2 with > 5 significance, precise mass measurement of Bs2 • First observation of BsDs(2536)mnX decay and mesurement of its Br • Updated LambdaB lifetime measurement