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

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B Physics at the Hadron Colliders Bs Meson and
New B Hadrons

• Introduction to B Physics
• Tevatron, CDF and DØ
• New B Hadrons
• Selected Bs Results
• Conclusion

BEACH 04
J. Piedra
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If not the Standard Model, What?

• Standard Model predictions validated to high
  precision, however

• 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?

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A Little History

• 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 its
  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

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B Hadrons

• 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
• Bs and?Lb Seen 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

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Example New Physics Opportunities

• Look at processes that are suppressed in the SM
• Bs(d) ? µµ- FCNC to leptons
• SM No tree level decay, loop level suppressed
• BF(Bs(d) ? µµ-) 3.5x10-9(1.0x10-10)
• G. Buchalla, A. Buras, Nucl. Phys. B398,285
• NP 3 orders of magnitude enhancement
  ?tan6ß/(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

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Bs and CKM 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

• 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

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The Tevatron
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• 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

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CDF Detector

• CDF Tracker
• Silicon 90cm long, 7 layer,
  rL00 1.3 - 1.6cm
• 96 layer drift chamber
  44 to 132cm
• Triggered Muon coverage ?lt1.0
• Displaced track trigger - hadronic B decays

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The Trigger

• Hadron collider Large production rates
• s(pp ? bX, y lt 1.0, pT(B) gt 6.0GeV/c) 30µb,
  10µb
• Backgrounds gt 3 orders of magnitude higher
• Inelastic cross section 100 mb
• Single and double muon based triggers and
  displaced track based triggers

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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

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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 bqq, q u,d JP SQ sqq
1/2 (Sb)
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?b Reconstruction

• 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

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?b Observation

• Observe Sb signal for all four expected Sb states

Sb- 59 ? 15 ? 7
Sb 32 ? 13 ? 4
Sb- 69 ? 18 ? 11
Sb 77 ? 17 ? 8

• Mass differences

m(Sb) - m(?b) 194.1 ? 1.2 ? 0.1MeV/c2
m(Sb) - m(Sb) 21.2 ? 1.9 ? 4 MeV/c2
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Orbitally Excited Bs Observation

• B sample selected using NN
• 58,000 Events

• Predictions 5830-5890, 10-20

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Bs(d) ? µµ- Method

• Rare decay that can be enhanced in Higgs, SUSY
  and other models
• Relative normalization search
• Measure the rate of Bs(d) ? µµ- 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

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Discriminating Variables

• 4 primary discriminating variables

• Mass Mmm
• CDF 2.5s window s 25MeV/c2
• CDF ?ct/ctBs
• ?a fB fvtx in 3D
• Isolation pTB/( ?trk pTB)
• CDF, ?, ?a and Iso used in
  likelihood ratio
• Unbiased optimization
• Based on simulated signal and data sidebands

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Bs(d) ? µµ- Search Results

• CDF Result 1(2) Bs(d) candidates observed
  consistent with background expectation

Decay Total Expected Background Observed
CDF Bs 1.27 0.36 1
CDF Bd 2.45 0.39 2

• Combined with D0(first 2fb-1 result)

• CDF 1 Bs result 3.0?10-6

PRD 57, 3811 1998
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Bs ? µµ Physics Reach

• Excluded at 95 CL (CDF result only)
• BF(Bs ? ??- ) 1.0x10-7
• Dark matter constraints

L. Roszkowski et al. JHEP 0509 2005 029

• Strongly limits specific SUSY models SUSY SO(10)
  models
• Allows for massive neutrino
• Incorporates dark matter results

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CMU Seminar
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New Physics in ?? Bs

• ?? 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

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?? Bs Bs ?KK-

• Bs,Short,Light ? CP even
• Bs,Long,Heavy ? CP odd

• CP Even Lifetimes in Bs ?KK-

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Bs Results ?? Bs

• 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

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Bs Direct CP Violation

• 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

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B0 Direct CP Violation
-0.107 ? 0.018 0.007-0.004

• Hadron colliders competitive with B factories!

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Bs 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

Lipkin, Phys.Lett. B621 (2005) 126
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Bs Mixing Overview
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• 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)
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Bs Mixing A Real Event

• CDF event display of a mixing event

Bs ? Ds-?, where Ds- ? ??-, ? ? KK-
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Bs Oscillations

• 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
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Bs Mixing Signals

• Fully reconstructed decays Bs ? Ds?(2?), where
  Ds ? ??, KK, 3?
• Also partially reconstructed decays
  one
  particle missing
• Semileptonic decays Bs ? DslX,
  where
  l e,?

Decay Candidates
Bs ? Ds?(2?) 5600
Bs ? Ds-?, Bs ? Ds- ? 3100
Bs ? DslX 61,500
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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

Tag Performance(?D2)
CDF OST 1.8
CDF SST 3.7(4.8)
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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

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Bs Mixing Results
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Bs Mixing Results
Key Features Result
Sen 95CL 31.3ps-1
Sen ?A(_at_17.5ps-1) 0.2
A/?A 6
Prob. Fluctuation 8x10-8
Peak value ?ms 17.75ps-1
PRL 97, 242003 2006
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Bs Mixing CKM Triangle
?ms 17.77 ? 0.10 (stat) ? 0.07 (syst) ps-1
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B Physics Conclusion

• 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 accompli
shed!
?ms 17.77 ? 0.10 (stat) ? 0.07 (syst) ps-1
-0.18
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