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

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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

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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

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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

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The Results!

M. Herndon

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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)

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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

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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

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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

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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

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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

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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

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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

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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

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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

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B0: Direct CP Violation

Hadron colliders competitive with B factories!

M. Herndon

-0.107 0.018 +0.007-0.004

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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

M. Herndon

Lipkin, Phys.Lett. B621 (2005) 126

BR(Bs K) = (5.0 0.75 1.0) x 10-6

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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!

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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

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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

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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

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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

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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