# Presentation: 759579

## B Physics at the Hadron Colliders: Physics of the Bs Meson

**J. Piedra**

*B* Physics at the Hadron Colliders: Physics of the *B**s* Meson

- Introduction to *B**s* Physics
- Tevatron, CDF and DØ
- Selected* B**s** *Results
- Tevatron and LHC Prospects
- Conclusion

## If not the Standard Model, What?

- Standard Model predictions validated to high precision, however

**M. 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
- Where is the Antimatter?
- Why is the observed universe mostly matter?

**FNAL Academic Lectures**

## Searches For New Physics

- How do you search for new physics at a collider?
- Direct searches for production of new particles
- Particle-antipartical annihilation
- Example: the top quark
- Indirect searches for evidence of new particles
- Within a complex process new particles can occur virtually

**M. Herndon**

- Tevatron is at the energy frontier and
-     a data volume frontier: ~2 billion B and Charm events on tape
- So much data that we can look for some very unusual processes
- Where to look
- Many weak processes involving *B* hadrons are very low probability
- Look for contributions from other low probability processes – Non Standard Model

## 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

- 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

- A Little History

- Bound state of up or down quarks with 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

**M. Herndon**

## Physics of Neutral Mesons

**M. Herndon**

- New physics(at the time) of neutral particles and antiparticles
*K**0* and *K**0*
- Interacted differently with weak and strong force.  Different eigenstates
- Strong force quark eigenstates: *K**0* and *K**0*
- Weak force mass and CP eigenstates: *K**0**S* and *K**0**L*
- The Schrödenger equation
- H not diagonal
*K**0* and *K**0** *not mass eigenstates

- -

- -

- -

## Physics of Neutral Mesons

- New states mass eigenstates
- Weak force mass and CP eigenstates: *K**0**S* and *K**0**L *explained
- m = 2M12 and width difference 

**M. Herndon**

- Treat the particle and anti-particle as one two state system               (Gelmann, Pais)

## Classical Analogue

**M. Herndon**

- Coupled spring system
- Start the system with one spring moving and over time it will evolve to a state where the other spring is moving and then back again.

## Oscillations

**M. Herndon**

- Time dependence

- Given a pure *K**0* state at t = 0

- Then at time t

## Why?

**M. Herndon**

- The flavor changing weak interaction is necessary                                  to get from *K**0* to *K**0*
- The weak force provides the coupling between the states that leads to the oscillations
- Also the CP eigenstates *K**S* and *K**L* are not changed by the weak force making them the weak force eigenstates

- -

## Neutral Kaons

**PR 103, 1901 (1956)**

- Very Rare decays observed in the Kaon system:

- BF(K0L →μμ-) = 7.3x10-9

- BF(K0L →-) = 2.1x10-3

**M. Herndon**

## 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 

- Translation between strong and weak eigenstantes
- Sets magnitude of flavor changing decays: Strange type kaons to down type pions

- CKM Physics

**M. Herndon**

- Several unitarity relationships to preserve probability
- b quark relationship the most interesting
- Largest CP violating parameter
- Best place to look for explanations for mater-antimatter asymmetry

## B quark unitarity relationship
Can be expressed as triangle in the complex plane

- Can be expressed as triangle in the complex plane

*B**s* and CKM Physics

**M. Herndon**

- Mixing strength set by *V**ts* parameter

**Pierini,***** et al.*****,**

## Physics of the Bs Meson

- Physics of the *B**s* Meson

- Look at processes that are suppressed in the SM
*B**s(d)* →μμ-: FCNC to leptons
- SM: No tree level decay,  loop level suppressed
- BF(*B**s(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**
*B**s* 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

**M. Herndon**

## New physics and the Bs Meson
Very interesting place to look for new physics(in our time)                      Higgs physics couples to mass so B mesons are interesting
Same program.  Rare decays, CP violation, , oscillations
State of our knowledge on the Bs last year
The Bs seen: known about since UA1 experiment in 1987.
In fact know to oscillate extremely fast!
SS vs OS leptons
However
Oscillation not directly seen
 not measured
CP violation not directly seen
Most interesting rare decys not seen

- Very interesting place to look for new physics(in our time)                      Higgs physics couples to mass so *B* mesons are interesting
- Same program.  Rare decays, CP violation, , oscillations
- State of our knowledge on the *B**s* last year
- The *B**s* seen: known about since UA1 experiment in 1987.
- In fact know to oscillate extremely fast!
- SS vs OS leptons
- However
- Oscillation not directly seen
-  not measured
- CP violation not directly seen
- Most interesting rare decys not seen

*B**s* Mesons

**M. Herndon**

## With the first evidence of the Bs meson we knew it oscillated fast.
How fast has been a challenge for a generation of experiments.

- How fast has been a challenge for a generation of experiments.

*B**s* Oscillations

**Amplitude method: Fourier scan for the mixing frequency**

**M. Herndon**

## 1.96TeV pp collider
Excellent performance and  improving each year
Record peak luminosity in 2007: 2.7x1032sec-1cm-2

- Excellent performance and  improving each year
- Record peak luminosity in 2007: 2.7x1032sec-1cm-2

- The Tevatron

- CDF/DØ Integrated Luminosity
- ~1fb-1 with good run requirements through 2005, now ~2fb-1
- All critical systems operating including silicon
- Doubled data in 2005                    almost double again in 2006

- -

**M. Herndon**

## CDF and DØ Detectors

- 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 Real CDF Detector

**M. Herndon**

**Wisconsin Colloquium**

## The Trigger

- Hadron collider: Large production rates
- σ(*pp → bX, |y| *< 1.0, pT(B) > 6.0GeV/c) = ~30μb, ~10μb
- Backgrounds: > 3 orders of magnitude higher
- Inelastic cross section ~100 mb
- Single and double muon based triggers and displaced track based triggers

**M. Herndon**

## Combining together excellent detectors and accelerator performance
Ready to pursue a full program of Bs physics

Today...
Bs → μμ
 Bs and CP violation
Direct CP violation
Bs Oscillations

- Ready to pursue a full program of *B**s* physics
- Today...
*B**s** **→ *μμ
-  *B**s* and CP violation
- Direct CP violation
*B**s* Oscillations

- The Results!

**M. Herndon**

## Bs(d) → μ+μ- Method

*B**s(d)** *→ μ+μ-* *Method

**M. Herndon**

- Relative normalization search
- Measure the rate of *B**s(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 *B**s* s for a given pT

- 400pb-1

## Discriminating Variables

**M. Herndon**

- Mass M
- CDF: 2.5σwindow: σ = 25*MeV/c**2*
- DØ: 2σwindow: σ = 90*MeV/c**2*
- CDF λ=cτ/cτBs, DØ Lxy/Lxy
- α : |φ**B** – φvtx| in 3D
- Isolation: pTB/( trk + pTB)
- CDF, λ, α and Iso:                     used in likelihood ratio
- D0 uses optimized cuts
- Optimization
- Unbiased optimization
- Based on simulated signal and data sidebands

- 4 primary discriminating variables

## Bs(d) → μ+μ- Search Results

- CDF 1 *B**s* result:    3.010-6
- BaBar *B**d* result:    8.310-8(90%)

*B**s(d)** *→ μ+μ-* *Search* *Results

**M. Herndon**

- CDF Result: 1(2) *B**s(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 |
| D0 Bs | 4+2.2 ± 0.7 | 4+?? |

- PRL 94, 221803 2005

- D0 Result: with 300pb-1 4 events.         700pb-1 still blind - expected limit:

- PRD 57, 3811 1998

## New Physics in  Bs

- New Physics in  *B**s*

**M. Herndon**

-  *B**s* Width-lifetime difference between eigenstantes *B**s,Short,Light** ** CP even       **B**s,Long,Heavy** ** CP odd*
- New physics can contribute in penguin diagrams

- Measurements
- Directly measure lifetimes in *B**s* *J*/ Separate CP states by angular    distribution and measure lifetimes
- Measure lifetime in *B**s*  *K**+ **K**-*                   CP even state
- Search for *B**s** *→ *D**s*(*)*D**s*(*)                                  CP even state                                                May account for most of the lifetime-width difference

##  Bs Method: Bs J/

-  *B**s* Method: *B**s* *J*/

- Directly measure lifetimes in *B**s* *J*/
- Separate CP states by angular distribution and measure lifetimes
- A0 = S + D wave  P even
- A|| = S + D wave  P even
- A = P wave  P odd

*  **B**s,Short,Light** ** CP even*
*  **B**s,Long,Heavy** ** CP odd*

- DØ Run II Preliminary

**M. Herndon**

##  Bs Results: Bs J/

-  *B**s* Results: *B**s* *J*/

**M. Herndon**

- Putting all the measurements together

- Assuming no CP violation

- DØ Run II Preliminary

- DØ Run II Preliminary

##  Bs CP Violation Results

-  *B**s* CP Violation Results

**M. Herndon**

- Allowing for CP Violation

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

- Combine with searches for CP violation in semileptonic *B* decays

- U. Nierste hep-ph/0406300

## Bs: Direct CP Violation

*B**s*: Direct CP Violation

- Direct CP violation expected to be large in some *B**s* decays
- Some theoretical errors cancel out in *B**0*, *B*s 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**

## B0: Direct CP Violation

*B**0*: Direct CP Violation

- Precision between  Babar and Bell: Hadron colliders competitive with B factories at their own game!

**M. Herndon**

## Bs: Direct CP Violation

*B**s*: 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

## Bs Mixing: Overview

*B**s* Mixing: Overview

**M. Herndon**

- Measurement of the rate of conversion from matter to antimatter: *B**s** **** B**s*
- Determine b meson flavor at production, how long it lived, and flavor at decay

*B**s*

- -

- p(t)=(1 ± D cos mst)

**tag  **

- to see if it changed!

## Bs Mixing: A Real Event

*B**s* Mixing: A Real Event

**M. Herndon**

- CDF event display of a mixing event

*B**s** **** D**s**-*+,  where *D**s**-** **** *-,   *K**+**K**-*

## Bs Mixing: Signals

*B**s* Mixing: Signals

**M. Herndon**

- Fully reconstructed decays: *B**s** **** D**s*(2),  where *D**s** **** *, *K***K*, 3
- Also partially reconstructed decays:                                                            one particle missing, but can still tell                                                         how far the particle flew.
- Semileptonic decays: *B**s** **** D**s**lX,  where l* =* e*,:                                        D0 includes *D**s** **** K*0s*K*

| Decay | Candidates |
| --- | --- |
| CDF Bs  Ds(2) | 5600 |
| CDF Bs  Ds-*+, Bs  Ds- + | 3100 |
| CDF Bs  DslX | 61,500 |
| D0    Bs  DslX | 41,000(+1600) |

## Bs Mixing: Flavor Tagging

*B**s* Mixing: Flavor Tagging

**M. Herndon**

- D0 Opposite side tag(OST): Combined Jet finding, b vertex  and lepton tag
- Information combined in a likelihood ratio
- 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 *B**0* oscillation analysis
- SST calibrated using MC and kaon finding performance validated in data

| Tag | Performance(D2) |
| --- | --- |
| D0    OST | 2.48  0.21  0.07% |
| CDF OST | 1.8% |
| CDF SST | 3.7%(4.8%) |

## Bs Mixing: Proper Time Resolution

*B**s* 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**

## Bs Mixing: DØ Results

*B**s* Mixing: DØ Results

| Key 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 |

**M. Herndon**

- PRL 97, 021802 2006

## Bs Mixing: Results

*B**s* Mixing: Results

## Bs Oscillations: Expected Sensitivity

- L00s primary effect is to improve proper time resolution
- Improves proper time resolution by 20% from 109fs to 87fs

## Bs Mixing: Results

*B**s* 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 |

- PRL 97, 242003 2006

## Bs Mixing: CKM Triangle

*B**s* Mixing: CKM Triangle

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

## Bs Results - New Physics

*B**s* Results - New Physics

**M. Herndon**

- Many new physics models that predict observable effects in flavor physics
- Consider a SUSY GFV model: general rather than minimal flavor violation
- Makes predictions for Non Standard model BF(*B**s* →μμ-) and ms
- Basically corrects quark mass terms with sqark-gluino loop terms in a general way
- Size of effects depends on tan and mA

**M. Herndon**

- hep-ph/0604121

##              Bs and CPV in Bs J/ 

-              *B**s* and CPV in *B**s* *J*/* *

**M. Herndon**

- Sensitivity for s in tagged and untagged analysis

## 2s in Bs J/ 

- 2s in *B**s* *J*/

**M. Herndon**

- Time independent measurement
- D0 analyzed 1fb-1
- CDF will have a 1fb-1 measurement with comparable sensitivity
- Can use TTT trigger as well(20% overlap)
- Time dependent analysis
- A key measurement that builds on the work of the mixing measurement
- Needs precision vertexing
- Needs large sample with low background
- Needs flavor tagging
- Use many modes
- Also comparable sensitivity

## What Else?

**M. Herndon**

- Consider *B* factory sin2 in charmonium vs. s penguin decays
- ccs vs css: Polarization and 2s
- Equivalent test is *B**s* *J*/  vs. *B**s*  (sss)
- Larger sample than used for similar angular analysis at the *B* factories

- 40 events
- In 360 pb-1

## LHCb 

- LHCb

**M. Herndon**

## LHCb 2s in Bs J/ 

- LHCb *2****s* in *B**s* *J*/

**M. Herndon**

- Key detector performance considerations

|  | Tevatron | LHCb |
| --- | --- | --- |
| Luminosity | 1fb-1/year | 2fb-1/year |
| ct | 87fs | 33fs |
| Tagging | 2.5-4.8% | 7-9% |

- Time dependent analysis should be very good!
- 0.1 accuracy on        Tevatron currently 0.4 from one 1fb-1 analysis

## Bs Physics Conclusion

*B**s* Physics Conclusion

**M. Herndon**

- Tevatron making large gains in our understanding of *B**s* Physics
- Concentrating on areas where there might be hints of new physics
- New stringent limits on rare decays:
- Precise measurement of  *B**s*
- On the hunt for direct CP violation
- First measurements of ms

- Factor of 30
-  improvement
-  over run 1

- And first look at the
-  CP violating phase

- -0.18

- One of the primary
-  goals of the
- Tevatron
- accomplished!

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

- 2.5