BEACH 04J. Piedra1 B Physics at the Hadron Colliders: B s Meson and New B Hadrons Introduction to B Physics Tevatron, CDF and DØ New B Hadrons Selected B s Results Conclusion Matthew Herndon, April 2007 University of Wisconsin Stony Brook Particle Physics Seminar

2 If not the Standard Model, What? Standard Model predictions validated to high precision, however Look for new physics that could explain these mysteries Look at weak processes which have often been the most unusual M. Herndon 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 fails to answer many fundamental questions

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 sec 3 A Little History Rich ground for studying new physics 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 s d K0K0 M. Herndon

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 B s seen: by UA1 experiment in Should oscillate B s  and  b Seen: by the LEP experiments and Tevatron Run 1 Some decays seen However B s oscillation not directly seen  not measured CP violation not directly seen Most interesting rare decays not seen No excited B s or heavy b baryons observed 4 B Hadrons b s A fresh area to look for new physics! M. Herndon b u d

5 Example New Physics Opportunities Look at processes that are suppressed in the SM B s(d) →  μ  μ - : FCNC to leptons SM: No tree level decay, loop level suppressed BF(B s(d) →  μ  μ - ) = 3.5x10 -9 (1.0x ) G. Buchalla, A. Buras, Nucl. Phys. B398,285 NP: 3 orders of magnitude enhancement  tan 6 β/(M A ) 4 Babu and Kolda, PRL 84, 228 B s 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 B , 2004, one example of many Closely Related:  and CP violation M. Herndon Z' sm value Hadron colliders have many opportunities to look for New Physics

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 6 B s and CKM Physics Unitarity relationship for b quarks CP violating phase Also in higher order terms Several unitarity relationships b quark relationship the most interesting Largest CP violating parameter B s oscillations measures most poorly understood side of the triangle Best place to look for explanations for mater-antimatter asymmetry

1.96TeV pp collider Excellent performance and improving each year Record peak luminosity in 2007: 2.8x10 32 sec -1 cm -2 7 The Tevatron 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 - B physics benefits from more data M. Herndon TRIGGERS ARE CRITICAL

CDF Tracker Silicon: 90cm long, 7 layer, r L00 = cm 96 layer drift chamber 44 to 132cm Triggered Muon coverage: |η|<1.0 Displaced track trigger - hadronic B decays 8 CDF Detector EXCELLENT TRACKING:TIME RESOLUTION EXCELLENT TRACKING: EFFICIENCY EXCELLENT TRACKING: MASS RESOLUTION M. Herndon

9 The Trigger Hadron collider: Large production rates σ(pp → bX, |y| 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 TRIGGERS ARE CRITICAL 2 Billion B and Charm Events on Tape M. Herndon

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

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

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

13  b Observation M. Herndon Observe  b signal for all four expected  b states Mass differences b-b- 59  15  7 b+b+ 32  13  4  b -* 69  18  11  b +* 77  17  8 m(  b ) - m(  b )  1.2  0.1MeV/c 2 m(  b * ) - m(  b ) 21.2  1.9  4 MeV/c 2 > 5 significance

14 Orbitally Excited B s ** Observation B+ sample selected using NN 58,000 Events Predictions: , Masses 94.8  23.4 B s2 * 36.4  9.0 B s  0.44  0.35 MeV/c 2 m(B s2 *) - m(B s1 )  0.2  0.6 MeV/c 2 m(B s1 ) > 5 significance

15 B s(d) → μ + μ - Method M. Herndon Rare decay that can be enhanced in Higgs, SUSY and other models Relative normalization search Measure the rate of B s(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 B s  s for a given p T 9.8 X 10 7 B + events

16 Discriminating Variables M. Herndon Mass M  CDF: 2.5σ  window: σ = 25MeV/c 2 CDF λ=cτ/cτ Bs  α : |φ B – φ vtx | in 3D Isolation: p TB /(  trk + p TB ) CDF, λ,  α and Iso: used in likelihood ratio Unbiased optimization Based on simulated signal and data sidebands 4 primary discriminating variables

CDF 1 B s result: 3.0  B s(d) → μ + μ - Search Results M. Herndon CDF Result: 1(2) B s(d) candidates observed consistent with background expectation Decay Total Expected Background Observed CDF B s 1.27 ± CDF B d 2.45 ± BF(B s   +  - ) < 10.0x10 -8 at 95% CL BF(B d   +  - ) < 3.0x10 -8 at 95% CL PRD 57, Combined with D0(first 2fb -1 result): BF(B s   +  - ) < 5.8x10 -8 at 95% CL

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

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

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

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

22 B s : Direct CP Violation Direct CP violation expected to be large in some B s decays Some theoretical errors cancel out in B 0, B s 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 First Observations

23 B 0 : Direct CP Violation Hadron colliders competitive with B factories! M. Herndon 

24 B s : Direct CP Violation 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 M. Herndon Lipkin, Phys.Lett. B621 (2005) 126 BR(B s  K  ) = (5.0  0.75  1.0) x 10 -6

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

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

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

28 B s Mixing: Signals M. Herndon Fully reconstructed decays: B s  D s  (2  ), where D s  , K*K, 3  Also partially reconstructed decays: one particle missing Semileptonic decays: B s  D s lX, where l = e,  : DecayCandidates B s  D s  (2  ) 5600 B s  D s -*  +, B s  D s -  B s  D s lX61,500

29 B s Mixing: Flavor Tagging M. Herndon 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 B 0 oscillation analysis SST calibrated using MC and kaon finding performance validated in data SST and OST compared - cross calibration Tag Performance(  D 2 ) CDF OST1.8% CDF SST3.7%(4.8%)

30 B s 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

31 B s Mixing: Results March 2005 Nov 2005: Add D s - 3  and lower momentum D s - l + March 2006: Add L00 and SST April 2006: Use 1fb -1 DataAdd PID and NNs

32 B s Mixing: Results M. Herndon Key FeaturesResult Sen: 95%CL31.3ps -1 Sen:  A -1 ) 0.2 A/  A 6 Prob. Fluctuation8x10 -8 Peak value:  m s 17.75ps -1 A >5  Observation! PRL 97, Can we see the oscillation? 2.8THz

CDF 33 B s Mixing: CKM Triangle |V td | / |V ts | =  (stat + syst) (lat. QCD)  m s =  0.10 (stat)  0.07 (syst) ps -1

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