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B Physics at the Hadron Colliders: B s Meson and New B Hadrons

This seminar discusses the search for new physics at the hadron colliders, focusing on Bs mesons and new B hadrons. Topics include gravity, high energy behavior, grand unification, dark matter, and more.

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B Physics at the Hadron Colliders: B s Meson and New B Hadrons

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  1. B Physics at the Hadron Colliders: Bs Meson and New B Hadrons Matthew Herndon, April 2007 University of Wisconsin Stony Brook Particle Physics Seminar • Introduction to B Physics • Tevatron, CDF and DØ • New B Hadrons • Selected BsResults • Conclusion BEACH 04 J. Piedra 1

  2. If not the Standard Model, What? Standard Model fails to answer many fundamental questions Look for new physics that could explain these mysteries Look at weak processes which have often been the most unusual • Gravity not a part of the SM • What is the very high energy behaviour? • At the beginning of the universe? • Grand unification of forces? • Dark Matter? • Astronomical observations of indicate that there is more matter than we see • Baryogenesis and Where is the Antimatter? • Why is the observed universe mostly matter? • Standard Model predictions validated to high precision, however M. Herndon 2

  3. A Little History d s Rich ground for studying new physics K0 • Everything started with kaons • Flavor physics is the study of bound states of quarks. • Kaon: Discovered using a cloud chamber in 1947 by Rochester and Butler. • Could decay to pions with a lifetime of 10-10 sec • Bound state of up or down quarks with a new particle: the strange quark! • Needed the weak force to understand it’s interactions. • Neutron kaons were some of the most interesting kaons • What was that new physics? New particles, Rare decays, CP violation, lifetime/decay width differences, oscillations M. Herndon 3

  4. B Hadrons s b b u d A fresh area to look for new physics! • New physics and the b Hadrons • Very interesting place to look for new physics(in our time) Higgs physics couples to mass so b hadrons are interesting • Same program. New Hadrons, Rare decays, CP violation, , oscillations • State of our knowledge on Heavy b Hadrons last year • Hints for Bs seen: by UA1 experiment in 1987. Should oscillate • BsandLbSeen: by the LEP experiments and Tevatron Run 1 • Some decays seen • However • Bs oscillation not directly seen •  not measured • CP violation not directly seen • Most interesting rare decays not seen • No excited Bs or heavy b baryons observed M. Herndon 4

  5. Example New Physics Opportunities Z' sm value Hadron colliders have many opportunities to look for New Physics • Look at processes that are suppressed in the SM • Bs(d)→μ+μ-: FCNC to leptons • SM: No tree level decay, loop level suppressed • BF(Bs(d)→μ+μ-) = 3.5x10-9(1.0x10-10) G. Buchalla, A. Buras, Nucl. Phys. B398,285 • NP: 3 orders of magnitude enhancement tan6β/(MA)4 Babu and Kolda, PRL 84, 228 • Bs Oscillations • SM: Loop level box diagram • Oscillation frequency can be calculated using electroweak SM physics and lattice QCD • NP can enhance the oscillation process, higher frequencies Barger et al., PL B596 229, 2004, one example of many • Closely Related:  and CP violation M. Herndon 5

  6. Bs and CKM Physics CP violating phase Also in higher order terms Unitarity relationship for b quarks • Much of our knowledge of the flavor physics can be expressed in the CKM matrix • Translation between strong and weak eigenstantes • Sets magnitude of flavor changing decays: Strange type kaons to down type pions • Several unitarity relationships • b quark relationship the most interesting • Largest CP violating parameter • Bs oscillations measures most poorly understood side of the triangle • Best place to look for explanations for mater-antimatter asymmetry 6

  7. The Tevatron TRIGGERS ARE CRITICAL B physics benefits from more data - • 1.96TeV pp collider • Excellent performance and improving each year • Record peak luminosity in 2007: 2.8x1032sec-1cm-2 • CDF Integrated Luminosity • ~2fb-1 with good run requirements through now • All critical systems operating including silicon • Have doubled the data twice in the last few years M. Herndon 7

  8. CDF Detector EXCELLENT TRACKING: EFFICIENCY EXCELLENT TRACKING: MASS RESOLUTION EXCELLENT TRACKING:TIME RESOLUTION • CDF Tracker • Silicon: 90cm long, 7 layer, rL00 =1.3 - 1.6cm • 96 layer drift chamber 44 to 132cm • Triggered Muon coverage: |η|<1.0 • Displaced track trigger - hadronic B decays M. Herndon 8

  9. The Trigger 2 Billion B and Charm Events on Tape TRIGGERS ARE CRITICAL • Hadron collider: Large production rates • σ(pp → bX, |y| < 1.0, pT(B) > 6.0GeV/c) = ~30μb, ~10μb • Backgrounds: > 3 orders of magnitude higher • Inelastic cross section ~100 mb • Single and double muon based triggers and displaced track based triggers M. Herndon 9

  10. The Results! • Combining together an excellent detector and accelerator performance • Ready to pursue a full program of B hadron physics • Today… New Heavy B Hadrons Bs→ μμ Bs and CP violation Direct CP violation Bs Oscillations M. Herndon 10

  11. New B Baryons • Lb only established b baryon - LEP/Tevatron • Tevatron: large cross section and samples of Lb baryons • First possible heavy b baryon: • Predictions from HQET, Lattice QCD, potential models, sum rules… = 3/2+(Sb*) Sb: b{qq}, q = u,d; JP = SQ + sqq = 1/2+ (Sb) M. Herndon 11

  12. bReconstruction • Strategy: • Establish a large sample of decays with an optimized selection and search for:b+Lb+ b: Nb = 3184 • Estimate backgrounds: • Random Hadronization tracks • Other B hadrons • Combinatoric • Extract signal in combined fit of Q distribution M. Herndon 12

  13. bObservation > 5s significance • Observe Sb signal for all four expected Sb states • Mass differences M. Herndon 13

  14. Orbitally Excited Bs** Observation > 5s significance Bs1 36.4  9.0 Bs2* 94.8  23.4 • Masses m(Bs1) 5821.4  0.2  0.6 MeV/c2 m(Bs2*) - m(Bs1) 10.20  0.44  0.35 MeV/c2 • B+ sample selected using NN • 58,000 Events • Predictions: 5830-5890, 10-20 14

  15. Bs(d)→ μ+μ-Method 9.8 X 107B+ events • Rare decay that can be enhanced in Higgs, SUSY and other models • Relative normalization search • Measure the rate of Bs(d)→ μ+μ-decays relative to BJ/K+ • Apply same sample selection criteria • Systematic uncertainties will cancel out in the ratios of the normalization • Example: muon trigger efficiency same for J/ or Bss for a given pT M. Herndon 15

  16. Discriminating Variables 4 primary discriminating variables • Mass Mmm • CDF: 2.5σwindow:σ = 25MeV/c2 • CDF λ=cτ/cτBs • α : |φB – φvtx| in 3D • Isolation: pTB/( trk + pTB) • CDF, λ, α and Iso: used in likelihood ratio • Unbiased optimization • Based on simulated signal and data sidebands M. Herndon 16

  17. Bs(d)→ μ+μ-SearchResults BF(Bs +- ) < 10.0x10-8 at 95% CL BF(Bd +- ) < 3.0x10-8 at 95% CL BF(Bs +- ) < 5.8x10-8 at 95% CL CDF Result: 1(2) Bs(d)candidates observedconsistent with background expectation Combined with D0(first 2fb-1 result): CDF 1 Bs result: 3.010-6 PRD 57, 3811 1998 M. Herndon 17

  18. Bs→μμ: Physics Reach A close shave for the theorists BF(Bs +- ) < 5.8x10-8 at 95% CL • Excluded at 95% CL (CDF result only) • BF(Bs +- ) = 1.0x10-7 • Dark matter constraints • Strongly limits specific SUSY models: SUSY SO(10) models • Allows for massive neutrino • Incorporates dark matter results L. Roszkowski et al. JHEP 0509 2005 029 CMU Seminar M. Herndon 18

  19. New Physics in Bs CP Violation will change this picture Many Orthogonal Methods! • Bs Width-lifetime difference between eigenstantes Bs,Short,Light CP even Bs,Long,Heavy CP odd • New physics can contribute in penguin diagrams • Measurements • Directly measure lifetimes in BsJ/ Separate CP states by angular distribution and measure lifetimes • Measure lifetime in Bs K+ K-CP even state • Search for Bs→ Ds(*)Ds(*)CP even state May account for most of the lifetime-width difference M. Herndon 19

  20. Bs: BsK+K- Bs = -0.08  0.23  0.03 ps-1 Bs = 1.53  0.18  0.02 ps • Bs,Short,Light CP even • Bs,Long,Heavy CP odd • CP Even Lifetimes in BsK+K- M. Herndon 20

  21. Bs Results: Bs Non 0 Bs Bs = 0.12  0.08  0.03 ps-1 Bs = 0.17  0.09 ps-1  = NP + SM = -0.70 +0.47-0.39 • Assuming no CP violation • Putting all the measurements together, including D0 • Allowing CP violation U. Nierste hep-ph/0406300 • Consistent with SM  Bs = 0.10  0.03 SM = -0.03 - +0.005 M. Herndon 21

  22. Bs: Direct CP Violation First Observations • Direct CP violation expected to be large in some Bs decays • Some theoretical errors cancel out in B0, Bs CP violation ratios • Challenging because best direct CP violation modes, two body decays, have overlapping contributions from all the neutral B hadrons • Separate with mass, momentum imbalance, and dE/dx M. Herndon 22

  23. B0: Direct CP Violation -0.107  0.018 +0.007-0.004 • Hadron colliders competitive with B factories! M. Herndon 23

  24. Bs: Direct CP Violation BR(Bs  K) = (5.0  0.75  1.0) x 10-6 • Good agreement with recent prediction • ACP expected to be 0.37 in the SM • Ratio expected to be 1 in the SM • New physics possibilities can be probed by the ratio Lipkin,Phys.Lett. B621 (2005) 126 M. Herndon 24

  25. Bs Mixing: Overview - • Measurement of the rate of conversion from matter to antimatter: Bs Bs • Determine b meson flavor at production, how long it lived, and flavor at decay to see if it changed! tag Bs p(t)=(1 ± D cos mst) M. Herndon 25

  26. Bs Mixing: A Real Event Precision measurement of Positions by our silicon detector Charge deposited particles in our drift chamber Momentum from curvature in magnetic field Hits in muon system B flight distance • CDF event display of a mixing event Bs Ds-+, where Ds--,   K+K- M. Herndon 26

  27. Bs Oscillations ms > 14.4 ps-1 95% CL expected limit (sensitivity) Run 2 Tevatron experiments built to meet this challenge > 2.3 THz • With the first evidence of the Bs meson we knew it oscillated fast. • How fast has been a challenge for a generation of experiments. Amplitude method: Fourier scan for the mixing frequency M. Herndon 27

  28. Bs Mixing: Signals • Fully reconstructed decays: Bs Ds(2), where Ds, K*K, 3 • Also partially reconstructed decays: one particle missing • Semileptonic decays: Bs DslX, where l = e,: M. Herndon 28

  29. Bs Mixing: Flavor Tagging • CDF OST: Separate Jet with b vertex and lepton tags • Tags then combined with a Neural Net, NN • CDF Same side tag(SST): Kaon PID • Taggers calibrated in data where possible • OST tags calibrated using B+ data and by performing a B0 oscillation analysis • SST calibrated using MC and kaon finding performance validated in data • SST and OST compared - cross calibration M. Herndon 29

  30. Bs Mixing: Proper Time Resolution • Measurement critically dependent on proper time resolution • Full reconstructed events have excellent proper time resolution • Partially reconstructed events have worse resolution • Momentum necessary to convert from decay length to proper time M. Herndon 30

  31. Bs Mixing: Results March 2005 April 2006: Use 1fb-1 Data Add PID and NNs Nov 2005: Add Ds-3 and lower momentum Ds-l+ March 2006: Add L00 and SST 31

  32. Bs Mixing: Results A >5 Observation! Can we see the oscillation? 2.8THz PRL 97, 242003 2006 M. Herndon 32

  33. Bs Mixing: CKM Triangle CDF |Vtd| / |Vts| = 0.2060  0.0007 (stat + syst) +0.0081(lat. QCD) -0.0060 ms = 17.77  0.10 (stat)  0.07 (syst) ps-1 33

  34. B Physics Conclusion BF(Bs +- ) < 5.8x10-8 at 95% CL ACP(Bs  K) = 0.39  0.15  0.08 • CDF making large gains in our understanding of B Physics • First new heavy baryon, Sb, observed • New stringent limits on rare decays: • On the hunt for direct CP violation • First measurements of ms Factor of 50 improvement over run 1 2.5 One of the primary goals of the Tevatron accomplished! ms = 17.77  0.10 (stat)  0.07 (syst) ps-1 -0.18 M. Herndon 34

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