Transcript Searches for FCNC Decays Bs(d) → μ+μ-

Flavour Physics and Dark Matter
Introduction
Selected Experimental Results
Impact on Dark Matter Searches
Conclusion
Matthew Herndon
University of Wisconsin
Dark Side of the Universe 2007, Minneapolis Minnesota
Why Beyond Standard Model?
Standard Model predictions validated to high precision, however
Standard Model fails to answer many fundamental questions
Many of those questions come from Astrophysics and Cosmology
Gravity not a part of the SM
What is the very high energy behaviour?
At the beginning of the universe?
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?
Connection between collider based physics and
astrophysics becomes more interesting each year
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Searches For New Physics
How do you search for new physics at a collider?
Direct searches for production of new particles
Particle-antipartical annihilation: top quark
Indirect searches for evidence of new particles
Within a complex process new particles can occur virtually
Tevatron is at the energy frontier
Tevatron and b factories are at a data volume frontier
billions 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
Rare Decays, CP Violating Decays and Processes such as Mixing
Present unique opportunity to find new physics
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B Physics Beyond the SM
Look at processes that are suppressed in the SM
Excellent place to spot small contributions from non SM contributions
The Main Players:
Bs(d) → μ+μSM: No tree level decay
b  s
˜

Penguin decay
New Players
˜

Bs Oscillations
B  

Same particles/vertices occur in both B decay diagrams

and in dark matter scattering or annihilation
diagrams
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˜

˜

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The B Factories
CDF
BABAR
BELLE
EXCELLENT PARTICLE ID
EXCELLENT TRACKING:
TIME RESOLUTION
EXCELLENT MUON DETECTION
D0
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b → s
Look at decays that are suppressed in the
Standard Model: b → s
Classic b channel for searching for new physics
Inclusive decay easier to calculate but still difficult
New physics can enter into the
loop(penquin)
Decay observed
Now a matter of precision
measurement and precision
calculation of the SM rate
New calculation by Misiak et. al.
NNLO calucation - 17 authors
and 3 years of effort
BR(b → s) = 3.15  0.23 x 10-4
PRL 98 022002 2007
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One of the best indirect search channels at the b factrories
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b → s
Measure the inclusive branching ratio from
the photon spectrum
Backgrounds from continuum production
and other B decays
Continuum backgrounds suppressed using event
shapes or reconstruction the other B
o and  reconstructed and suppressed
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Bs(d) → μ+μLook at decays that are suppressed in the
Standard Model: Bs(d) → μ+μFlavor changing neutral currents(FCNC) to leptons
No tree level decay in SM
Loop level transitions: suppressed
CKM , GIM and helicity(ml/mb): suppressed
SM: BF(Bs(d) → μ+μ-) = 3.5x10-9(1.0x10-10)
G. Buchalla, A. Buras, Nucl. Phys. B398,285
New physics possibilities
Loop: MSSM: mSugra, Higgs Doublet
3 orders of magnitude enhancement
Rate tan6β/(MA)4
Babu and Kolda, Phys. Rev. Lett. 84, 228
Tree: R-Parity violating SUSY
Small theoretical uncertainties. Easy to spot new physics
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One of the best indirect search channels at the Tevatron
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Bs(d) → μ+μ- Method
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
9.8 X 107 B+ events
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
+
400pb-1

N(B+)=2225
BR(B +  J /K + )  BR(J /   + )
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Discriminating Variables
4 primary discriminating variables
Mass M
CDF: 2.5σ window: σ = 25MeV/c2
DØ: 2σ window: 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
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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
BF(Bd  +- ) < 3.0x10-8 at 95% CL
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
D0 Result: First 2fb-1 analysis!
BF(Bs  +- ) < 9.3x10-8 at 95% CL
Worlds Best Limits!
Combined:
BF(Bs  +- ) < 5.8x10-8 at 95% CL
CDF 1 Bs result:
PRD 57, 3811 1998
3.010-6
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Bs →
+
μ μ:
Physics Reach
BF(Bs  +- ) < 5.8x10-8 at 95% CL
A close shave for the
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
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Typical example of SUSY Constraints
However, large amount of recent work
specifically on dark matter
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B Physics and Dark Matter
B Physics constraints impact dark matter in two ways
Dark matter annihilation rates
Interesting for indirect detection experiments
Annihilation of neutralinos
Dark matter scattering cross sections
Interesting for direct detection experiments
Nucleon neutralino scattering cross sections
Models are (n,c)MSSM models with constraints to simplify the parameter space:
Key parameters are tanβ and MA as in the flavour sector along with m1/2
Two typical programs of analysis are performed
Calculation of a specific property: Nucleon neutralino scattering cross sections
Constraints from Bs(d) → μ+μ- and b  s as well as g-2, lower bounds on the Higgs mass, precision
electroweak data, and the measured dark matter density.
General scan of allowed SUSY parameter space from which ranges of allowed
values can be extracted
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Results can then be compared
to experimental sensitivities
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
SUSY and Dark Matter
What’s consistent with the constraints?
There are various areas of SUSY
parameter space that are allowed by
flavour, precision electroweak and WMAP
Stau co-annihilation
m˜  m˜
Funnel 
˜

˜

2m˜  m
A
Bulk Region
Low m0 and m1/2, good for LHC
Focus Point
Large m0 neutralino becomes higgsino like
Enhanced Higgs exchange scattering diagrams
TeV
H. Baer et. al.
Disfavoured by g-2, but g-2 data is controversial
Informs you about what types of dark
matter Interactions are interesting
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~
Flavour Constraints on m
New analysis uses all available flavour constraints
Bs → μ+μ-, b  s, Bs Oscillations, B  
Later two results only 1 year old
J. Ellis, S. Heinemeyer, K. Olive, A.M Weber
and G. Weiglein hep-ph/0706.0652
CMSSM - constrained so that
SUSY scalers and the Higgs
and the gauginos have a
common mass at the GUT scale:
m0 and m1/2 respectively
Focus Point
Stau co-annihilation
This region favoured
because of g-2
Definite preferred
neutralino masses
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Bs → μ+μ- and Dark Matter
Bs → μ+μ- correlated to dark matter searches
CMSSM supergravity model
Bs → μ+μ- and neutralino scattering cross sections are both a strong
functions of tanβ S. Baek, D.G. Cerdeno Y.G. Kim, P. Ko, C. Munoz, JHEP 0506 017, 2005
In high tanβ(tanβ ~ 50), positive μ, CDM allowed
Current bounds on Bs → μ+μ- exclude parts of
the parameter space for direct dark matter detection
R. Austri, R. Trotta, L. Roszkowski, hep-ph/0705.2012
More general scan in m0, m1/2 and A0, allowed region
CDF Paper Seminar 2007
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B Physics and Dark Matter
Putting everything together including most recent theory work on b  s
Analysis shows a preference for the
Focus Point region, g-2 deweighted
Higgsino component of Neutralino is
enhanced.
Enhances dominant Higgs exchange
scattering diagrams
Interesting relative to light Higgs
searches at Tevatron and LHC
Probability in some regions
has gone down
R. Austri, R. Trotta, L. Roszkowski, hep-ph/0705.2012
Current experiments starting to probe interesting regions
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However…
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Current Xenon 10 Results
Liquid Xenon detector
Multiple modules
Excluded by new Bs → μ+μ-
Excluding part of the high probability
region - 60 live day run!
Xenon 10 Preliminary
R. Austri, R. Trotta, L. Roszkowski
Current best limits
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Dark Matter Prospects
From dmtools.brown.edu
Just considering upgrades of
the two best current
experiments and LUX.
Excluded by new Bs → μ+μ-
Prospects for dark matter
detection look good in CMSSM
models constrained by collider
data!
Perhaps find both Dark
Matter and Bs → μ+μ-
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Conclusions
Collider experiments are providing a wealth of data on Flavour physics
as well as direct searches and precision electroweak data
These data can be used to constrain the masses and scattering cross
sections of dark matter candidates
Constrained MSSM models indicate that dark matter observation may
be within reach for current or next generation experiments! If Bs → μ+μis there as well.
A simulations observation of direct(or indirect) evidence
for new physics at a collider and Cold Dark Matter would
reveal much about the form of the new physics
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