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International Symposium of Multiparticle Dynamics 2007 09 Aug 2007

International Symposium of Multiparticle Dynamics 2007 09 Aug 2007. B Spectroscopy at the Tevatron. Tania Moulik (University of Kansas) On behalf of CDF & DØ collaboration. Accelerator chain. 3 Km. 6 Km. 150 m. Protons : LINAC  Booster  Main Injector  Tevatron

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International Symposium of Multiparticle Dynamics 2007 09 Aug 2007

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  1. International Symposium of Multiparticle Dynamics 200709 Aug 2007 B Spectroscopy at the Tevatron Tania Moulik (University of Kansas) On behalf of CDF & DØ collaboration Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  2. Accelerator chain 3 Km 6 Km 150 m • Protons :LINAC Booster  Main Injector  Tevatron 400 MeV8 GeV  150 GeV  ~1.00 TeV • Antiprotons : 120 GeV protons (MI)  Ni Target  antiprotons  debuncher+accumulator+recycler Tevatron Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  3. Overview of Detectors Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  4. B spectroscopy Motivation • QCD simplifies in the limit of one heavy quark mass  Heavy Quark effective field theory (HQET). Mass scale for heavy baryons different from quark confinement scale L ~ 400 MeV governing physics of light hadrons. • mt, mb, mc >> LQCD >> ms, mu, md • Heavy baryons good way to study non-perturbative QCD (Quark interactions inside hadrons described by non-perturbative QCD) • HQET successful in describing Qq systems. Continue to test it for Qqq systems. • Features of HQET: • Treat heavy quark as static source of color field. • In case of baryons, view Light quarks forming a diquark pair and independent of the heavy quark in the limit of infinite heavy quark mass and it looks the same for any flavor or spin orientation of the heavy quark • Also test Heavy baryon predictions from other theoretical models (approximations to QCD): • 1/Nc expansion, sum rules, lattice QCD Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  5. Experimental timeline of heavy B baryons • For a long time only known heavy B baryon was Lb. • Semileptonic decays observed at LEP between 1992-1998 and also at Tevatron. • Hadronic decay modes (Fully reconstructed == Measure mass precisely) • (J/YL) (1991)@UA1 • (1997)@CDF • Lcp (2006) @ CDF and continued to be studied at Tevatron. • Recent discoveries at Tevatron of Sb and Xb, and the excited B states lead to an exciting new era of testing theories describing quark systems with a heavy baryon. • Potential to discover other new B baryons, …and so on… Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  6. The quest for b Baryons Host of hadron discoveries led Enrico Fermi to exclaim "Had I foreseen that, I would have gone into botany" • Light diquark system : spin 0 (L) (I=0, Jp=0-) / spin 1 (S) (I=1, Jp=1+) state • state (0+)  heavy Quark (1/2+), Sstate (1+)  heavy Quark (1/2+) Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  7. Mass predictions and hierarchies • Why are L and S masses different? • S (uus) – L (uds) mass difference believed to be due to difference between u-d and u-s hyperfine interactions : • And other predictions : Hyperfine splittings Zeldovich, Sakharov, Sov. J. Nucl. Phys. 4(1967) 283 Karliner, Lipkin, hep-ph/0307243, Phys. Lett. B 575, 249(2003) Predicted mass hierarchy: M(Λb)< M(b) < M(b) Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  8. Observation of Sb • In Sb light quarks in symmetric state • Together with heavy quark leads to doublet of baryons • Ground state S decays strongly to L-type baryons (antisymmetric configuration of quarks) emitting pions. Look for Sb in decay mode Lbp. Number of theoretical predictions: Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  9. Start with constructing Lb Then, Search for narrow resonances in the mass difference distribution Backgrounds: tracks from Lb fragmentation (e.g. hadronization of the b quark) and underlying event. Physics background, B0 D-p+; D- p-K+p- Also B0’s from B** decays. Optimize cuts with Sb signal region blinded. Sb Lbp, Lb Lcp, Lc p K p Lb ct(PDG) = 422 mm, Cut requirement: ct (Lb) > 250 mm 5.565 < m(Lb) < 5.670 GeV Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  10. Fit to breit-wigner convoluted with double gaussian. Width of breit-wigner : No isospin splitting sensitivity Measure average Sb Results Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  11. Observation of Xb (dsb) Vertex Prob c2 > 1 % Track with higher mom. Assumed pion 1.05 GeV < M (pp) < 1.125 GeV At most 2 hits in tracker before pp vertex. Imp. Param sig. > 3(both tracks) At least > 4 (for one track) Vertex Prob c2 > 1 % pT (m) > 1.5 GeV 2.80 GeV < M (mm) < 3.35 GeV pT (J/Y) > 5 GeV Imp. Param sig. > 3(pion track) Decay length (L) > 4 * uncertainty Decay length (X) > 4 * uncertainty Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  12.  p   Special techniques.. • For particles like the b-, usual impact parameter cut requirement for track reconstruction could result in missing the  and proton tracks from the  and - decays. • At DØ entire J/Y dataset was processed with “special” extended tracking: • Impact parameter cut from 2.5 cm  10.0 cm • Maximum acceptance angle Df 0.08 rad  0.2 rad • At CDF X candidate tracks are refitted, with Si hit requirements. →p- -   Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  13. Xb Results 15.2  4.4 Likelihood Fit Results : M (DØ) = 5774  11(stat.) 15 (syst.)MeV -- [1] M (CDF)= 5792.9  2.4(stat.) 1.7 (syst.) GeV ) – [2] (Theory : 5.793 - 5.814) 17.5  4.3 [1] PRL 99, 1052001 (2007) [2] arXiv:0707.0589 Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  14. Observation B1 and B2* • Among B mesons, • Only ground 0- states B+,B0,Bs,Bc • and excited 1- state B* considered established. • Quark models predict 2 broad and 2 narrow P-states: • Broad states difficult to distinguish  Width ~ 100 MeV (Decay through an S wave). • Narrow states easier to identify  Width ~ 10 MeV (Decay through D wave) M..Di Pierro and E. Eichten, Phys. Rev. D 64 (2001) Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  15. Observation B1 and B2* • Look for mesons in decay modes • Reconstruct Look for p track from primary vertex. Combine with B+ Plot Breit-wigner convoluted with gaussian. Resolution in DM determined from simulation PDG, J. Phys. G 33 1 (2006) Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  16. Observation B1 and B2* Unable to resolve the B2* decaying through B* and emission of g and through B. Masses agree to within 1 s Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  17. Observation of Bs* • Analysis similar to previous mode • Look for the decay B*s2B+K- Where is B*s2B*K ? should be here Claim : Suppressed due to L=2 orbital angular momentum and small mass difference D0 does not observe the Bs1 peak. Would be interesting to look at more data. Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  18. Bs* Interpretation and Theory • Theory predicts equal branching ratios of Bs2*  B*+K- and B+K-. Experimentally should be observed as resonance displaced to lower DM by photon energy 45.78+-0.35 MeV. • Rate supressed by a factor (No signal expected with current statistics) • What about Bs1  B*K+? • In (bd) system, M(B2*) – M(B1) = 26.2+-3.1+-0.9, ..Applying to Bs system… • Expect Bs1 = 5813 MeV i.e. < M(B*)+M(K-) (5819 MeV)…In this case, no Bs1 signal expected. C.M. Momentum of K in B*K decay C.M. momentum of K in B K decay Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  19. Results Bs* Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

  20. B Quest began … and continues @ Fermilab Celebrating 30 years of the b quark discovery @ Fermilab 1977 A fitting anniversary celebration: Discovery of new B baryons…and the search goes on…! Discovery of b quark : The Upsilon (bb). Tania Moulik, B Spectroscopy at Tevatron, ISMD 2007

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