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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. - PowerPoint PPT Presentation
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BEACH 04 J. Piedra 1
B Physics at the Hadron Colliders:
Bs Meson and New B Hadrons
Introduction to B Physics
Tevatron, CDF and DØ
b Baryon
Selected Bs Results
Conclusion
Matthew Herndon, March 2007University of Wisconsin
APS April Meeting
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 unusualM. 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 and had a very long lifetime:
10-10 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
sd
K0
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 Bs seen: by UA1 experiment in 1987.
Bsandb 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
4
B Hadrons
bs
A fresh area to look for new physics!
M. Herndon
bu d
1.96TeV pp collider
Excellent performance and improving
each year
Record peak luminosity in 2007:
2.8x1032sec-1cm-2
5
The Tevatron
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
-
B physics benefits from more dataM. Herndon
TRIGGERS ARE CRITICAL
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
6
CDF and DØ Detectors
DØ Tracker
Silicon and Scintillating Fiber
Tracking to |η|<2
New L0 on beam pipe!
Triggered Muon coverage: |η|<2.0
EXCELLENT TRACKING:
TIME RESOLUTION
EXCELLENT TRACKING: EFFICIENCY
EXCELLENT TRACKING: MASS RESOLUTION
M. Herndon
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
7
The Results!
M. Herndon
8
New B Hadrons
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; JP = SQ + sqq
= 3/2+(b*)
= 1/2+ (b)
9
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: Nb = 3184
10
b Observation
M. Herndon
Observe b signal for all four
expected b states
> 5 significance level
Mass differences
b- 59 15 7
b+ 32 13 4
b-* 69 18 11
b+* 77 17 8
m(b) - m(b) 194.1 1.2 0.1MeV/c2
m(b*) - m(b) 21.2 1.9 4 MeV/c2
11
Bs(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 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
€
BF(Bs → μ +μ−) =(Ncand − Nbg )
α BsεBs
•α
B +εB +
NB +
•fu
f s
•
BR(B+ → J /ψK +) • BR(J /ψ → μ +μ−)
400pb-1
9.8 X 107 B+ events
N(B+)=2225
12
Discriminating Variables
M. Herndon
Mass M
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
4 primary discriminating variables
CDF 1 Bs result: 3.010-6
13
Bs(d) → μ+μ- Search Results
M. Herndon
CDF Result: 1(2) Bs(d) candidates observed
consistent with background expectation
Worlds Best Limits!
Decay
Total Expected Background
Observed
CDF Bs
1.27 ± 0.36 1
CDF Bd
2.45 ± 0.39 2
D0 Bs
0.8 ± 0.2 1.5 ± 0.3
3
BF(Bs +- ) < 10.0x10-8 at 95% CL
BF(Bd +- ) < 3.0x10-8 at 95% CL
D0 Result: First 2fb-1 analysis!
BF(Bs +- ) < 9.3x10-8 at 95% CL
PRD 57, 3811 1998
Combined:
BF(Bs +- ) < 5.8x10-8 at 95% CL
14
New Physics in Bs
M. Herndon
Bs Width-lifetime difference between eigenstates
Bs,Short,Light CP even Bs,Long,Heavy CP odd
New physics can contribute in penguin diagrams
Many Orthogonal Methods!
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
€
Bsmeas = ΔΓBs
CPCons • cos(δφs), δφs = δφSM + δφNP
€
δφs ≡ 2β s
15
Bs Results: Bs J/
M. Herndon
Non 0 Bs
Putting all the measurements together
Bs = 0.12 0.09 0.02 ps-1
Assuming no CP violation
DØ Run II PreliminaryDØ Run II Preliminary
D0: PRL 98, 121801 2007
16
Bs CP Violation Results
M. Herndon
Allowing for CP Violation
€
Bsmeas = ΔΓBs
SMCPCons • cos(φSM + φNP )
Consistent with SM Bs = 0.10 0.03 SM = -0.03 - +0.005
Combine with searches for CP
violation in semileptonic B decays
Bs = 0.17 0.09 ps-1
= NP + SM = -0.70 +0.47-0.39
U. Nierste hep-ph/0406300
D0: hep-ex/0702030
17
Bs: Direct CP ViolationDirect 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
First Observations
18
B0: Direct CP Violation
Hadron colliders competitive with B factories!
M. Herndon
-0.107 0.018 +0.007-0.004
19
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
M. Herndon
Lipkin, Phys.Lett. B621 (2005) 126
BR(Bs K) = (5.0 0.75 1.0) x 10-6
20
Bs Mixing: Overview
M. Herndon
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
Bs
-
p(t)=(1 ± D cos mst)
tag to see if it changed!
21
Bs Mixing
M. Herndon
Bs
tag
Tag Performance(D2)
D0 OST 2.48 0.21 0.07%
CDF OST 1.8%
CDF SST 3.7%(4.8%)
Decay Candidates
CDF Bs Ds(2) 5600
CDF Bs Ds-*+, Bs Ds
- + 3100
CDF Bs DslX 61,500
D0 Bs DslX 41,000(+1600)
Large samples, good flavor tagging, great time resolution
22
Bs Mixing: DØ ResultsKey Features Result
Sen: 95%CL
16.5ps-
1
Sen: A(@17.5ps-1)
0.7
A/A 1.6
Prob. Fluctuation
8%
Peak value: ms
19ps-1
Limits: 17-21ps-1 @90CL
One experiment with more sensitivity than the whole generation of experiments before!
M. HerndonPRL 97, 021802 2006
23
Bs Mixing: Results
M. Herndon
Key Features Result
Sen: 95%CL
31.3ps-
1
Sen: A(@17.5ps-1)
0.2
A/A 6
Prob. Fluctuation
8x10-8
Peak value: ms
17.75ps-1
A >5 Observation!
PRL 97, 242003 2006
Can we see the oscillation?
2.8THz
Tevatron
24
Bs Mixing: CKM Triangle
|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
25
B Physics Conclusion
M. Herndon
BF(Bs +- ) < 9.3-10x10-8 at 95% CL
Factor of 30
improvement
over run 1
Bs = 0.12 0.09 ± 0.02 ps-1
And first look at the
CP violating phase
-0.18One of the primary
goals of the
Tevatron
accomplished!ms = 17.77 0.10 (stat) 0.07 (syst) ps-1
ACP(Bs K) = 0.39 0.15 0.08 2.5
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