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
Matthew Herndon, April 2007
University of Wisconsin
BEACH 04
Stony Brook Particle
Physics Seminar
J. Piedra
1
If not the Standard Model, What?
Standard Model predictions validated to high precision, however
Standard Model fails to answer many fundamental questions
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?
Look for new physics that could explain these mysteries
Look at weak processes which have often been the most unusual
M. Herndon
2
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 it’s interactions.
K0
Neutron kaons were some of the most interesting kaons
Rich ground for studying new physics
d
What was that new physics? New particles, Rare decays, CP
s
violation, lifetime/decay width differences, oscillations
M. Herndon
3
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
s
b
Some decays seen
However
Bs oscillation not directly seen
 not measured
b
CP violation not directly seen
u
d
Most interesting rare decays not seen
No excited Bs or heavy b baryons observed
A fresh area to look for new physics!
M. Herndon
4
Example New Physics Opportunities
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
Z'
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
Hadron colliders have many opportunities to look for New Physics
M. Herndon
sm
value
5
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
CP violating phase

A (   i ) 
 Vud Vus Vub   1   / 2



2
2
  Vcd Vcs Vcb   

1  / 2
A
 + O(4 )

 Vtd V V   A3 (1    i )  A2
1

ts
tb  

2
VCKM
VudVub* + Vcd Vcb* + VtdVtb*  0
3
Also in higher
order terms
Unitarity relationship for b quarks
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
The Tevatron
-
1.96TeV pp collider
Excellent performance and improving
each year
Record peak luminosity in 2007:
2.8x1032sec-1cm-2
TRIGGERS ARE CRITICAL
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
7
CDF Detector
CDF Tracker
Silicon: 90cm long, 7 layer,
rL00 =1.3 - 1.6cm
96 layer drift chamber
44 to 132cm
EXCELLENT TRACKING: MASS RESOLUTION
EXCELLENT TRACKING: EFFICIENCY
EXCELLENT TRACKING:TIME RESOLUTION
Triggered Muon coverage: |η|<1.0
Displaced track trigger - hadronic B decays
M. Herndon
8
The Trigger
Hadron collider: Large production rates
σ(pp → bX, |y| < 1.0, pT(B) > 6.0GeV/c) = ~30μb, ~10μb
TRIGGERS ARE CRITICAL
Backgrounds: > 3 orders of magnitude higher
2 Billion B and Charm Events on Tape
Inelastic cross section ~100 mb
Single and double muon based triggers and displaced track based triggers
M. Herndon
9
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
New B Baryons
Lb only established b baryon LEP/Tevatron
Tevatron: large cross section
and samples of Lb baryons
First possible heavy b baryon:
= 3/2+(Sb*)
Sb: b{qq}, q = u,d; JP = SQ + sqq
= 1/2+ (Sb)
Predictions from HQET,
Lattice QCD, potential
models, sum rules…
M. Herndon
11
Sb Reconstruction
Strategy:
Establish a large sample of
decays with an optimized
selection and search for:
Sb+  Lb+
Lb: NLb = 3184
Estimate backgrounds:
Random Hadronization tracks
Other B hadrons
Combinatoric
Extract signal in combined fit of Q
distribution
M. Herndon
12
Sb Observation
Observe Sb signal for all
four expected Sb states
> 5s
significance
-
Sb
59  15  7
Sb+
32  13  4
Sb-*
69  18  11
Sb+*
77  17  8
Mass differences
m(Sb) - m(Lb)
194.1  1.2  0.1MeV/c2
m(Sb*) - m(Sb)
21.2  1.9  4 MeV/c2
M. Herndon
13
Orbitally Excited Bs** Observation
B+ sample selected using
NN
58,000 Events
Predictions: 5830-5890, 10-20
> 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
14
Bs(d) → μ+μ- Method
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
9.8 X 107 B+ events
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
(N cand  N bg )  B + B + f u
BF (Bs    ) 

 
 BsBs
NB +
fs
+

BR(B +  J /K + )  BR(J /   + )
M. Herndon
15
Discriminating Variables
4 primary discriminating variables
Mass M
CDF: 2.5σ window:
σ = 25MeV/c2
CDF λ=cτ/cτBs
α : |φB – φvtx| in 3D
Isolation: pTB/( Strk + pTB)
CDF, λ, α and Iso:
used in likelihood ratio
Unbiased optimization
Based on simulated signal
and data sidebands
M. Herndon
16
Bs(d) → μ+μ- Search Results
CDF Result: 1(2) Bs(d) candidates observed
consistent with background expectation
BF(Bs  +- ) < 10.0x10-8 at 95% CL
Decay
Total Expected
Background
Observed
CDF Bs
1.27 ± 0.36
1
CDF Bd
2.45 ± 0.39
2
BF(Bd  +- ) < 3.0x10-8 at 95% CL
Combined with D0(first 2fb-1 result):
BF(Bs  +- ) < 5.8x10-8 at 95% CL
CDF 1 Bs result:
3.010-6
PRD 57, 3811 1998
M. Herndon
17
Bs → μμ:Physics Reach
BF(Bs  +- ) < 5.8x10-8 at 95% CL
A close shave for the
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
theorists
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
CMU Seminar
M. Herndon
18
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
CPCons
Bsmeas  Bs
 cos( s ),  s   SM +  NP
CP Violation will
s  2s change
Measurements
this picture
Directly measure lifetimes in Bs J/
Separate CP states by angular
distribution and measure lifetimes
Measure lifetime in Bs  K+ KCP even state

Search for Bs → Ds(*)Ds(*)
CP even state
May account for most of the lifetime-width
difference
M. Herndon
Many Orthogonal Methods!
19
 Bs: Bs K+KCP Even Lifetimes in Bs K+K-
Bs,Short,Light  CP even
Bs,Long,Heavy  CP odd
 Bs = 1.53  0.18  0.02 ps
 Bs = -0.08  0.23  0.03 ps-1
M. Herndon
20
Bs Results:  Bs
Assuming no CP violation
 Bs = 0.12  0.08  0.03 ps-1
Non 0  Bs
Putting all the measurements together,
including D0
Allowing CP violation
 Bs = 0.17  0.09 ps-1
 = NP + SM = -0.70 +0.47-0.39
U. Nierste hep-ph/0406300
Consistent with SM  Bs = 0.10  0.03 SM = -0.03 - +0.005
M. Herndon
21
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
First Observations
M. Herndon
22
B0: Direct CP Violation
-0.107  0.018 +0.007-0.004
Hadron colliders competitive with B factories!
M. Herndon
23
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
Lipkin, Phys.Lett. B621 (2005) 126
New physics possibilities can be
probed by the ratio
M. Herndon
24
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
Bs Mixing: A Real Event
CDF event display of a mixing event
Bs  Ds-+, where Ds-  -,   K+KPrecision measurement of
Positions by our silicon detector
B flight distance
Charge deposited
particles in our drift chamber
Momentum from curvature
in magnetic field
Hits in muon system
M. Herndon
26
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.
> 2.3 THz
 ms > 14.4 ps-1 95% CL
expected limit
(sensitivity)
Amplitude method:
Fourier scan for the
mixing frequency
Run 2 Tevatron experiments built to meet this challenge
M. Herndon
27
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,:
Decay
Candidates
Bs  Ds(2)
5600
Bs  Ds-*+, Bs  Ds- +
3100
Bs  DslX
61,500
M. Herndon
28
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%)
M. Herndon
29
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
Bs Mixing: Results
March 2005
Nov 2005: Add Ds- 3
and lower momentum Ds-l+
March 2006: Add L00
and SST
April 2006: Use 1fb-1 Data
Add PID and NNs
31
Bs Mixing: Results
Key Features
Result
Sen: 95%CL
31.3ps-1
Sen: sA(
)
@17.5ps-1
A/sA
2.8THz
0.2
6
Prob. Fluctuation
8x10-8
Peak value: ms
17.75ps-1
A >5s Observation!
PRL 97, 242003 2006
Can we see the oscillation?
M. Herndon
32
Bs Mixing: CKM Triangle
CDF
ms = 17.77  0.10 (stat)  0.07 (syst) ps-1
|Vtd| / |Vts| = 0.2060  0.0007 (stat + syst) +0.0081
-0.0060(lat. QCD)
33
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:
Factor of 50
BF(Bs  +- ) < 5.8x10-8 at 95% CL
On the hunt for direct CP violation
ACP(Bs  K) = 0.39  0.15  0.08
improvement
over run 1
2.5s
First measurements of ms
-1
ms = 17.77  0.10
-0.18 (stat)  0.07 (syst) ps
M. Herndon
One of the primary
goals of the
Tevatron
accomplished!
34