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B Physics at the Hadron Colliders: B s Meson and New B Hadrons. Matthew Herndon, March 2007 University of Wisconsin APS April Meeting. Introduction to B Physics Tevatron, CDF and DØ  b Baryon Selected B s Results Conclusion. BEACH 04. J. Piedra. 1.

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b physics at the hadron colliders b s meson and new b hadrons
B Physics at the Hadron Colliders: Bs Meson and New B Hadrons

Matthew Herndon, March 2007

University of Wisconsin

APS April Meeting

  • Introduction to B Physics
  • Tevatron, CDF and DØ
  • b Baryon
  • Selected BsResults
  • Conclusion


J. Piedra


if not the standard model what
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


a little history
A Little History



Rich ground for studying new physics


  • 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 and had a very long lifetime: 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


b hadrons
B Hadrons






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.
    • 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


the tevatron
The Tevatron


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/DØ Integrated Luminosity
    • ~2fb-1 with good run requirements through end now
      • All critical systems operating including silicon
    • Have doubled the data twice in the last few years

M. Herndon


cdf and d detectors
CDF and DØ Detectors





  • CDF Tracker
    • Silicon |η|<2, 90cm long, rL00 =1.3 - 1.6cm
    • 96 layer drift chamber 44 to 132cm
  • Triggered Muon coverage: |η|<1.0
  • DØ Tracker
    • Silicon and Scintillating Fiber
    • Tracking to |η|<2
    • New L0 on beam pipe!
  • Triggered Muon coverage: |η|<2.0

M. Herndon


the results
The Results!
  • Combining together excellent detectors and accelerator performance
  • Ready to pursue a full program of B hadron physics
  • Today…

New Heavy b Baryons

Bs→ μμ

Bs and CP violation

Direct CP violation

Bs Oscillations

M. Herndon


new b hadrons
New B Hadrons
  • 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


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

M. Herndon


b observation
  • Observe Sb signal for all four expected Sb states
  • > 5s significance level
  • Mass differences

M. Herndon


b s d method
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


discriminating variables
Discriminating Variables

4 primary discriminating variables

  • Mass Mmm
    • CDF: 2.5σwindow:σ = 25MeV/c2
    • DØ: 2σwindow:σ = 90MeV/c2
  • CDF λ=cτ/cτBs, DØ Lxy/Lxy
  • α : |φB – φvtx| in 3D
  • Isolation: pTB/( trk + pTB)
  • CDF, λ, α and Iso: used in likelihood ratio
  • D0 additionally uses B and  impact parameters and vertex probability
  • Unbiased optimization
    • Based on simulated signal and data sidebands

M. Herndon


b s d search results
Bs(d)→ μ+μ-SearchResults

Worlds Best Limits!

BF(Bs +- ) < 10.0x10-8 at 95% CL

BF(Bd +- ) < 3.0x10-8 at 95% CL

BF(Bs +- ) < 9.3x10-8 at 95% CL

BF(Bs +- ) < 5.8x10-8 at 95% CL

CDF Result: 1(2) Bs(d)candidates observedconsistent with background expectation

D0 Result: First 2fb-1 analysis!


CDF 1 Bs result: 3.010-6

PRD 57, 3811 1998

M. Herndon


new physics in b s
New Physics in Bs

Many Orthogonal Methods!

  • Bs Width-lifetime difference between eigenstates 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


b s results b s j
Bs Results: BsJ/

Non 0 Bs

Bs = 0.12  0.09  0.02 ps-1

DØ Run II Preliminary

DØ Run II Preliminary

  • Putting all the measurements together
  • Assuming no CP violation

D0: PRL 98, 121801 2007

M. Herndon


b s cp violation results
Bs CP Violation Results

Bs = 0.17  0.09 ps-1

 = NP + SM = -0.70 +0.47-0.39

  • Allowing for CP Violation
  • Combine with searches for CP violation in semileptonic B decays

D0: hep-ex/0702030

  • Consistent with SM  Bs = 0.10  0.03 SM = -0.03 - +0.005

U. Nierste hep-ph/0406300

M. Herndon


b s direct cp violation
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


b 0 direct cp violation
B0: Direct CP Violation

-0.107  0.018 +0.007-0.004

  • Hadron colliders competitive with B factories!

M. Herndon


b s direct cp violation1
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


b s mixing overview
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!



p(t)=(1 ± D cos mst)

M. Herndon


b s mixing
Bs Mixing



  • Large samples, good flavor tagging, great time resolution

M. Herndon


b s mixing d results
Bs Mixing: DØ Results

One experiment with more sensitivity than the whole generation of experiments before!

Limits: 17-21ps-1 @90CL

PRL 97, 021802 2006

M. Herndon


b s mixing results
Bs Mixing: Results

A >5 Observation!

Can we see the oscillation?


PRL 97, 242003 2006

M. Herndon


b s mixing ckm triangle
Bs Mixing: CKM Triangle


|Vtd| / |Vts| = 0.2060  0.0007 (stat + syst) +0.0081(lat. QCD)


ms = 17.77  0.10 (stat)  0.07 (syst) ps-1


b physics conclusion
B Physics Conclusion

BF(Bs +- ) < 9.3-10x10-8 at 95% CL

Bs = 0.12  0.09 ± 0.02 ps-1

ACP(Bs  K) = 0.39  0.15  0.08

  • Tevatron making large gains in our understanding of B Physics
  • First new heavy baryon, Sb, observed
  • New stringent limits on rare decays:
  • Precise measurement of Bs
  • On the hunt for direct CP violation
  • First measurements of ms

Factor of 30


over run 1

And first look at the

CP violating phase



One of the primary

goals of the



ms = 17.77  0.10 (stat)  0.07 (syst) ps-1

M. Herndon