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B spectroscopy at the Tevatron

B spectroscopy at the Tevatron. Eduard De La Cruz Burelo CINVESTAV IPN Mexico On behalf of the CDF and D0 collaboration FPCP 2009, Lake Placid NY. Outline: CDF and DØ detectors B Physics @ Tevatron B c mass measurement Excited Bs mesons  b and  b observations Summary.

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B spectroscopy at the Tevatron

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  1. B spectroscopy at the Tevatron Eduard De La Cruz Burelo CINVESTAV IPN Mexico On behalf of the CDF and D0 collaboration FPCP 2009, Lake Placid NY Outline: • CDF and DØ detectors • B Physics @ Tevatron • Bc mass measurement • Excited Bs mesons • b and b observations • Summary August 28th, 2008 FPCP 2009 1 FPCP 2009

  2. CDF and DØ detectors • Important: • Triggering • Muons • Tracking/vertexing FPCP 2009

  3. B Physics @ Tevatron • Tevatron is an excellent place for B Physics • All B hadron species are produce: B+,B0,Bs,Bc, 0b, … • Total inelastic cross section (total)/(b)>103 • Need of smart selection beginning from triggers B spectroscopy status • Mesons: • B+, B0, Bs, Bc+ (established) • B* (established), • B**(CDF & DØ) • Bs** (CDF & DØ) • Baryons • b (established) • b+, and b*+(CDF) • b- , b- (CDF & DØ) FPCP 2009

  4. c Bc system study • Bc is not produced at b factories • Bc is a unique (heavy-heavy, q’s) system. • both b and c quark can decay weakly, with comparable probabilities • short (c-like) lifetimes observed • both DØ & CDF: ~ 0:45 ps • Experimentally challenging because of low production rate f(bBc) ~ 0.05% • Observed and lifetime measured by DØ and CDF in Bc J/l (l=,e) FPCP 2009

  5. Bc mass measurement • Exclusive reconstruction in Bc+J/+ • Optimization in B+J/K+ and Bc+J/+ Monte Carlo • Data of 1.3 fb-1integrated luminosity Signal significance > 5 PRL 101, 012001 (2008) FPCP 2009

  6. Bc mass measurement • Exclusive reconstruction in Bc+J/+ • Optimization in B+J/K+ • Data of 2.4 fb-1integrated luminosity B+J/K+ Bc+J/+ Signal significance > 8 PRL 100, 182002 (2008) FPCP 2009

  7. Bc mass predictions • Lattice QCD: • [a] Omitting sea quarks, (quenched approx.) • [b] Add 2+1 sea flavors, u,d as light as possible, and strangeness mass FPCP 2009

  8. L=1 q Excited (L=1) Bs mesons HQET: Spin of quarks decouple 1/2 3/2 jq=11/2 1+ 0+ 1/21/2 1/23/2 jq=1/2 are wide states, we cannot observe them jq=3/2 are narrow states (we can look for them) J=1/2jq 2+ 1+ FPCP 2009

  9. Search for narrow Bs** mesons • Reconstruct Bs**B(*)+K-, B*+B+ ( undetected), B+J/K+( CDF & DØ) and B+D0+ (CDF) Use Neural Network to optimize both B+ and Bs** FPCP 2009

  10. Excited (L=1) Bs mesons First direct observation of Bs2* M(Bs2*) = 5839.6  1.1(stat)  0.7 (syst) GeV/c2 PRL 100, 082002 (2008) First observation of Bs1 M(Bs1) = 5829.4  0.2  0.6 GeV/c2 M(Bs2*) = 5839.6  0.4  0.5 GeV/c2 PRL 100, 082001 (2008) Bs1 signal significance > 5 FPCP 2009

  11. When Tevatron Run II begun: from hep-ph/9406359 FPCP 2009

  12. During Tevatron Run II FPCP 2009

  13. + - p  -b - ~5 cm ~5 cm ~0.7 mm - - Search for b-J/(+-)- • Reconstruction procedure: • Reconstruct J/→+- • Reconstruct →p • Reconstruct → +  • Combine J/+  • Improve mass resolution by using an event-by-event mass difference correction • The optimization: • b→J/ decays in data • J/ + (fake from (p-)+ ) • Monte Carlo simulation of b-→J/+- Construct composite particle from . FPCP 2009

  14. Based on: • b→J/ decays in data • J/ + (fake from (p-)+ ) Background events from wrong-sign combinations ( Λ(p-) + ) b- Search optimization Final b selection cuts: • →p decays: • pT(p)>0.7 GeV • pT()>0.3 GeV • - → decays: • pT()>0.2 GeV • Transverse decay length>0.5 cm • Collinearity>0.99 • -bparticle: • Lifetime significance>2. (Lifetime divided by its error) FPCP 2009

  15. -b observation (DØ) Number of events: 15.2 ± 4.4 Mass: 5.774 ± 0.011(stat) GeV Width: 0.037 ± 0.008 GeV Signal Significance: We also measured: • Fit: • Unbinned extended log-likelihood fit • Gaussian signal, flat background • Number of background/signal events are floating parameters PRL 99, 052001 (2007) FPCP 2009

  16. -b observation (CDF) Also searched for in b-c0- M(b-) = 5792.9  2.5 (stat)  1.7 (syst) MeV/c2 Signal significance = 7.8 Updated 2009 mass measurement in G.Punzi talk PRL 99, 052002 (2007) FPCP 2009

  17. Comparison: Experiment/Theory DØ PRL 99, 052001 (2007) CDF PRL 99, 052002 (2007) FPCP 2009

  18. bss quarks combination Mass is predicted to be 5.94 - 6.12 GeV M(-b) > M(b) Lifetime is predicted to be 0.83<(-b)<1.67 ps Search for the -b(bss) FPCP 2009

  19. How do we look for it? + - p  -b - ~5 cm ~? ~3 cm - Similar K- FPCP 2009

  20. Analysis strategy • Events are reprocessed to increase reconstruction efficiency of long-lived particles. • Select J/ candidates • Yield is optimized by using proper decay length significance cuts. • Select p • Optimize yield by using multivariate techniques • Reconstruction of → + K • Combine J/ + (K+) • Keep blinded J/ +  combinations and optimize on J/ + (K+) • Improve mass resolution from 80 MeV to 34 MeV • Event per event mass correction • Perform as many test as possible in different background samples • Fix selection criteria and then apply them to J/ +  FPCP 2009

  21. BDT to select -K decays  decays removed FPCP 2009

  22. We compare MC signal vs wrong-sign background events. Final optimization FPCP 2009

  23. Nothing where nothing should be We check also high statistics MC samples No excess is observed in any control samples after selection criteria is applied to them. FPCP 2009

  24. Looking at right-sign combinations • After optimization: • <0.03 cm • J/ and  in the same hemisphere • pT(J/+)>6 GeV • Mass window for the search: 5.6 - 7 GeV Clear excess of events near 6.2 GeV FPCP 2009

  25. b- mass measurement • Fit: • Unbinned extended log-likelihood fit • Gaussian signal, flat background • Number of background/signal events are floating parameters N= 17.8 ± 4.9 (stat) ± 0.8(syst) Mass: 6.165 ± 0.010(stat) ± 0.013(syst)GeV Width fixed (MC): 0.034 GeV PRL 101, 232002 (2008) FPCP 2009

  26. Consistency check: Increase pT(B) Significance >6 FPCP 2009

  27. Cut Based Analysis (CBA) Number of signal events: 15.7 ± 5.3 Mean : 6.177 ± 0.015(stat) GeV Width fixed (MC): 0.034 GeV Signal significance: 3.9 • After remove duplicate events, we observe 25.5 ± 6.5 events. • Significance: 5.4 FPCP 2009

  28. Summary Many unique results coming from Tevatron: • First direct observation of Bs1 and Bs2* • Precise measurement of the Bc mass. • First observation of b- and b- baryons • Not shown here: • Precise B** mass measurement • First observation of b- and b*- baryons • Limits in b production • And many more results … http://www-d0.fnal.gov/Run2Physics/WWW/results/b.htm http://www-cdf.fnal.gov/physics/new/bottom/bottom.html FPCP 2009

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