Upload
teague
View
25
Download
1
Embed Size (px)
DESCRIPTION
Search for Supersymmetry Using Rare B 0 s(d) m + m - Decays at CDF Run II. Vyacheslav Krutelyov Department of Physics Texas A&M University HEP Seminar Dec 20, 2005 Fermilab. Motivations Standard Model Supersymmetry Br(B s μ + μ - ) in SM. Br(B s μ + μ - ) in SUSY - PowerPoint PPT Presentation
Citation preview
Search for Supersymmetry Using Rare B0
s(d)Decays
at CDF Run IIVyacheslav Krutelyov
Department of Physics
Texas A&M University
HEP SeminarDec 20, 2005
Fermilab
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 2
Outlines
MotivationsStandard ModelSupersymmetryBr(Bsμ+μ-) in SM.Br(Bsμ+μ-) in SUSY
Loops: large tan mSUGRA,SO(10) Tree: R-parity violating models
Analysis Strategy CDF Run II Dimuon Trigger Sample
Br(Bsμ+μ-) measurement. Ingredients. Likelihood discriminant Background estimate. Signal efficiency × acceptance Optimization. Results
SUSY implications. mSUGRA SO(10) RPV
Prospects for Bsμ+μ-
Summary.
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 3
Standard Model
+ Higgs
The SM describes the matter in terms of elementary particles
Quarks of 6 flavorsLeptons: charged (massive) and neutral (massless neutrinos)
and interactions are mediated by force carriers
Strong ↔ gluonsElectroweak broken (by Higgs) weak (W+ and Z0) and electromagnetic (photon)
withMasses defined by interaction with Higgs scalar
Quarks (except t) form hadrons: qqq (baryons)q-anti-q (mesons)
Bs (b anti-s), Bd (b anti-d) and B+ (u anti-b) are b-mesons with mass ~5.3GeV and lifetime ~1.6 ps will be often referred later
Hadrons change flavor only via W+ exchange
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 4
Standard Model (status)
SM describes all collider physics observations(has been for the past 20+ years) BUT: neutrinos have masses most of the matter in the Universe is not in SMSM does not include gravitySM has naturalness (hierarchy) problemsNeed for physics beyond the SM Supersymmetry is (one of) the best choice solves gauge hierarchy problem gives a candidate for dark matter can explain neutrino masses …
+ Higgs
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 5
Supersymmetry
LSP– Cold Dark Matter Candidate
SUSY Charged Current Stop L-R mixing2 Higgs Doublets: tan=vevu/vevd
•SUSY requires for each particle to be a superpartner•SM superpartners: squarks and sleptons (s=0); gauginos and higgsinos (s=1/2)•SUSY is broken at low energy
•MSSM: minimal SUSY SM extension (with 2 Higgs doublets)•EWSB w Higgs give masses
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 6
Importance of Bs(d)
Bs(d)is a Flavor Changing Neutral Current process (FCNC)Quarks b and s are of the same electric charge
hadronic state flavor change (b anti-s)(has no charge transfer
FCNC processes are the benchmarks of the theoryDefined the construction of the SMConstrain substantially any New Physics
bshas been a golden FCNC mode for years
Bs is suggested as a new golden FCNC mode
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 7
• In the Standard Model, the FCNC decay of B +- is heavily suppressed
910)9.05.3()( sBBR
• SM prediction is below the sensitivity of current experiments SM Expect to see 0 events at the Tevatron
(Buchalla & Buras, Misiak & Urban)
• Bd is further suppressed by CKM coupling (Vtd/Vts)2≈40
• Br(Bs) < 4.1×10-7 @ 90% CL ; D0 PRL 94 (2005) 042001 (240pb-1)
SM prediction
Any signal would indicate new physics!!
Bsin Standard Model
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 8
• In many SUSY models, the BR could be enhanced by many orders of magnitude:
For example: - MSSM: Br(B) is proportional to tan6 - GUT SO(10) models prefer tan ≈50 (Yukawa coupling
unification)
-BR could be as large as 10-1000 times the SM prediction
Could be observable at the Tevatron
Bin SUSY: large tan
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 9
’i23 i22
b
s
• Another example: R-Parity violating (RPV) SUSY•R-parity ↔ SUSY particles come in pairs
- Tree level diagram is allowed in R-parity violating (RPV) SUSY models. - No significant tandependence
- Enhancement depends stronglyon coupling constants (’
correspond to ijkqiqjk ’ijkliljk interactions
Could also be observable at the Tevatron
Bin SUSY: RPV tree
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 10
• New physics may enhance Bs and Bd differently
• Minimal-flavor-violation (MFV) assumption in SUSY yields SM relations between Bs and Bd Br(Bs):Br(Bd) ≈ (Vts/Vtd)2≈40
• Can observe both Bs and Bd: unique to Tevatron (Bd only at B-factories)
• CDF has the mass resolution to distinguish two decays, M≈23MeV : unique to CDF
• Either observation or null search, will provide important clues about possible scenarios of new physics beyond SM
Monte Carlo
M(Bs)-M(Bd)~90MeV
Bsand Bd
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 11
Bs(d)StrategyUse p anti-p collisions at 1.96 TeV at
Tevatron to produce Bs(d) mesons
B-hadrons are produced as a result of
(p anti-p)(b anti-b)Hadrons evolve out of b with N(B+):N(Bd
0):N(Bs0):N(b)=fu:fd:fs:fbar~4:4:1:1
N(Bs) = fs N(Hb) BR(Bs)
Use CDF detector to detect the muons from Bs(d)
of all Bs [N(Bs)] detect only
n(Bs)≡ () N(Bs)() – cceptance × fficiency
Hide signal data while choosing the best selections
Define N(Hb) from normalization mode
N(B+J/K+K+) = fu N(Hb) BR(B+K+)
BR(B+K+) ≈ 6×10-5
p
p_
ppbb_ _
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 12
z
y
x))2/ln(tan(
Central Drift Chamber (COT) < 1)
Silicon Vertex Detector
Central Muon Chambers: CMU, CMP (|| < 0.6)
Central Muon Extension: CMX (0.6< || < 1)
Components relevant to the analysis are highlighted
SuperconductingSolenoid (1.4T)
CDF II33o to 53o from ┴
0o to 33o from ┴
0o to 53o from ┴
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 13
Typical Dimuon Event
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 14
•Using 364pb-1 of data (Feb02 – Aug04) from Rare B di-muon triggers:- CMUCMU 2 muons 0o to 33o from ┴
- CMUCMX 1 muon 0o to 33o from ┴ 1 muon 33o to 53o from ┴ •CMUCMU and CMUCMX channels treated independently in this analysis (background and efficiencies are different)
Search region
Rare B di-muon triggersrequire additional cuts to reduce background relative to inclusive J/ di-muon trigger
Data Sample
Background is huge
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 15
Key elements in the analysis: - Construct discriminant to select Bs signal and suppress bgd
- MC simulation for signal and mass sidebands for bgd estimate
- understanding the background - accurately measure the acceptance and efficiency ratios
Analysis optimization: Figure of merit expected 90% C.L. upper limit Perform unbiased optimization
Overall picture: - Reconstruct di-muon events in the B mass window - Measure the branching ratio or set a limit - Normalize to B+J/ K+ decays
)()(
)()(
KBBRf
f
N
NBBR
s
u
B
totalB
totalBs
Bss
BsMeasurementIngredients
Nobs=Nbg+NBs
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 16
Selection Requires:• pT(B)>4 GeV && |y(B)|<1• pT(K+)>1GeV > 2well-measured displaced vertex
= proper decay length (B+) ≈502m]
B+K+ in rare B trigger Sample: N(CMUCMU) = 1767±59
N(CMUCMX) = 698±39
Count the # of B++-K+ candidates with |M-3097|<50 MeV/c2
)(3
Bp
McL D
CMUCMU
(m
Normalization mode: B+J/K+
MJ/
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 17
Pre-selection requires:• pT(B)>4 GeV && |y(B)|<1 • > 2 • well-measured displaced vertex
Bs Search Sample:N(CMUCMU) = 22459N(CMUCMX) = 14305
(completely Bgd dominated)
“Baseline” cuts select quality di-muons that should have passed the trigger,and have a well-measured vertex consistent with long-lived b-hadron decayto reject events that are clearly background (non-trigger or mis-reconstructed)
CMUCMU
Background shapes are linearfor both channels
[ (Bs) ≈468m]
BSignal Mode: “baseline selections”
Bd Bs
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 18
Signal vs Background
P
P P
L3D
x
y
BBss BBss R < 1 (< 57o)
z
gbb
c
_
c_ _
gq q
_ x
yGluon SplittingGluon Splittingg g bb bb
Gluon SplittingGluon Splittingg g bb bb
z
Backgrounds are random combinations of (fake)muonsThe best look-alike is the “gluon splitting”
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 19
Invariant +- mass, M|M-MB|<60 MeV/c2 (2.5)
sidebands: [4669, 5169] U [5469, 5969] MeV/c2 (0.50.5 GeV/c2)signal: |M-5279|<60 MeV/c2 (Bd
0) or |M-5279|<60 MeV/c2 (Bs0)
Proper decay-length (): displacement from production vtx
in B rest frame Isolation (Iso):
(fraction of pT from B within R=(2+2)1/2 cone of 1)
“pointing ()”:
(3D opening angle between Bs momentum and decay axis)
)(3
Bp
McL D
i iiTT
T
RpBp
BpIso
)1()(
)(
))(( 3DLBp
To select B events and suppress background use:
Discriminating Variables
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 20
cut cut
To further reduce Bgd, apply the additional cuts:
<0.70 rad
&&Iso > 0.50
eff(signal) ≈ 92%
This leaves in data:(4.7GeV < m < 6 GeV)
N(CMUCMU) = 6242
N(CMUCMX) = 4908
~x3 down in bkg but still…~1.3K in signal window
Discriminating Variables
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 21
• Use a likelihood ratio method:
ii
i
xPxPxP
ibis
isLH
)()(
)(
Ps/b is the probability for a given sig/bgd to have a valueof x, where i runs over all discriminating variables.
• The chosen variables (xi) are: - isolation (iso) - 3D pointing (),
- proper decay length probability [P()=exp(-/Bs)]
• Ps/b (PDFs) are constructed from the data sideband for background and Pythia MC for signal•LH has among the best discriminating power if xi are uncorrelated
Likelihood Ratio Discriminant)()(
)(),..(
1 xPxP
xPLH
bs
sNxx
analog of
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 22
yx
N
iii
xy
yyxx
N
1
)ˆ)(ˆ(
1
1
Correlations between discriminating variablesare negligible allows to reduce Stat uncertainty for expected bgd estimate
Correlations between variables for Bgd
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 23
CMU-CMU Signal and background PDFs for:
Isolation
Pointing angle
Proper decay lengthprobability
* Similar distributions for CMU-CMX
Likelihood PDFs
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 24
Likelihood ratio has strong discriminatingpower between signaland background
Likelihood Ratio: Signal vs Bgd
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 25
Extrapolate number of events in the side-bands tothe signal region to estimate expected background Assumes bgd events inside signal window look the same as outside
x-check this using MC and control samples Bhh (h=K decays are negligible
• Nbg = #events in signal region surviving all requirements
• NSB = #events in mass sidebands surviving pre-LH cuts
• Rmass = WidthSignal / WidthSideBand = 0.12•Assumes linear mass distribution
• RLH = fraction of bgd events expected to survive LH cut
LHmassSBbg RRNN
Estimate Background
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 26
Since discriminating variables are uncorrelated, use toy MCto estimate RLH based on input distributions from data SB
KS-Prob(CMUCMU)=11%KS-Prob(CMUCMX)=5%
Likelihood Ratio Data vs Toy MC
RLH*103
Cut CMU-CMU CMU-CMX
LH>0.85 24.5±0.5 22.6±0.5LH>0.92 13.0± 0.4 12.0±0.3LH>0.99 1.4±0.1 1.5±0.1
Likelihood Ratio Rejection from Toy MC
(Errors are stat only)
LH strongly suppresses bkg
Estimate Bgd Rejection by LH cut (RLH)
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 27
LHBs
KrecoBvtx
Bs
vtxB
recoBs
recoB
trigBs
trigB
Bs
B
B
B
s
1
)(
)(
• (B+/Bs) = 0.297 ± 0.008 (CMUCMU) = 0.191 ± 0.006 (CMUCMX)
• trig(B+/Bs) = 0.9997 ± 0.0016 (CMUCMU) = 0.9986 ± 0.0014 (CMUCMX)
• reco-(B+/Bs) = 1.00 ± 0.03 (CMUCMU/X)
• vtx(B+/Bs) = 0.986 ± 0.013 (CMUCMU/X)
• reco-K(B+) = 0.938 ± 0.016 (CMUCMU/X)
Pythia
MC
J/
Dat
a
DataM
C
Acceptance and Efficiency
≈1
)()(
)()(
KBBRf
f
N
NBBR
s
u
B
totalB
totalBs
Bss
var i
n opt
imiza
tion
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 28
LH(Bs) cut CMU-CMU CMU-CMX
LH>0.90 (68±1)% (66±1)%LH>0.92 (65±1)% (65±1)%LH>0.95 (59±1)% (60±1)%LH>0.98 (45±1)% (48±1)%LH>0.99 (35±1)% (39±1)%
• determined from Bs MC
• MC modeling checked by comparing LH(B+) between MC and sideband subtracted Data
(stat uncertainties only)
Efficiency of LH for Bs Signal
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 29
•To set a limit given observation nobs
•For a given BR and nbg the observed events nobs is given by Poisson distribution with nobs=BR + nbggiven actual nobs can use Bayesian method to extract P(BR| nobs,nbg, )
This properly accounts for uncertainties in nbg and Defines BRCL(nobs,nbg,) by CL = BR P(BR) d(BR)
Given nbg and can define a priori expected 90% CL upper limit by
To optimize: Vary event requirements to minimize BR90%CL
Optimization and Limit Setting
0
%90%90 ),,()|(n
bgCL
bgCL nnBRnnBR
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 30
• For optimization, scan: LH>0.90-0.99, pT(B)>4-6 GeV
• Assume 1 fb-1 of data Optimal cuts: LH>0.99 and pT(B)>4GeV
•Uncertainties are included in the limit calculation Dominant uncertainty is fs/fu from PDG ~ 15%(rel)
Fragmentation ratio (Bs/B+)
Optimization Result
CMUCMU CMUCMXLuminosity 364 pb-1 336 pb-1
SES (1.0±0.2) ×10-7 (1.5±0.3) ×10-7
Nbg 0.81 ± 0.12 0.66 ± 0.13BR90% CL 3.5×10-7 5.6×10-7
BR90% CL 2.0 ×10-7Bs
S
umm
ary
SES = BR for Nsignal=1
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 31
For optimized cuts of LH >0.99 and pT(B) > 4GeV and a 60 MeV window around world avg Bs(d) mass
Observed 0 event in the signal region!
Open Box
CMU-CMU Channel CMU-CMX Channel
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 32
Bs: 0 events observed yields a combined limit of: 1.5×10-7 @ 90% CL 2.0×10-7 @ 95% CL
Bd: 0 events observed yields a combined limit of: 3.9×10-8 @ 90% CL 5.1×10-8 @ 95% CL
Compare to:
Br(Bs) < 4.1×10-7 @ 90% CL ; D0 PRL 94 (2005) 042001 (240pb-1)
Br(Bs) < 5.8×10-7 @ 90% CL ; CDF PRL 93 (2003) 032001 (171pb-1)
Br(Bd) < 8.0×10-8 @ 90% CL ; BaBar PRL 94 (2005) 221803 (111fb-1)
Both CDF Bs and Bd results are ×2 better than the best published result
Limits Summary
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 33
• For mh~115GeV implies 10-8<Br(Bs)<3×10-7
Dedes, Dreiner, Nierste, PRL 87(2001) 251804
M0
[GeV
]
Excluded
Excluded
Excluded by this new resultneed ×3-5 improvement to exceed bsexclusion
Solid red = excluded by theory or experimentDashed red line = light Higgs mass (mh)Dashed green line = (a)susy (in units of 10-10)Black line = Br(Bs)
mSUGRA
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 34
• Within mSUGRA, if Bsis observed tan is large.
Kane, Kolda, Lannon hep-ph/0310042mSUGRA scan
2.1×10-7
Run II Tevatron95% CL
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 35
h2>0.13
m+
<10
4GeV
mh<
111G
eV
R. Dermisek et al., hep-ph/0304101
• New Br(Bs limit strongly disfavors this solution for mA< 500 GeV
Red regions are excluded by either theory or experimentsGreen region is the WMAP preferred regionBlue dashed line is the Br(Bs) contourLight blue region excluded by old Bs analysis
Excluded by thisnew result
SO(10) SUSY • tan()~50 constrained by unification of Yukawa coupling
• White region is not excluded
• Unification valid for small M1/2
(~500GeV)
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 36
B. Dutta et al, PLB 538 (2002) 121
’i23 i22
b
s
R-parity violating SUSY
• Possible to exclude phase space ~ independent of tan
• Exclusion strongly depends on the coupling.
Excluded
RPV SUSY Exclusion
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 37
•Optimistic: <BR>~ 1/Lumi•Additional handles on bgd exist: tighter muon ID (require CMP) calorimeter isolation additional 2D pointing use mass resolution model in LH•Combine with D0
BR(Bs) ≈ 1×10-8 at 90% CLis possible within Run II (by 09?)
•Can be measured at SM level by CMS at LHC after 2-3 years of data taking (by 10?)
Simplistic: no improvement to analysis scale Nbg and NB+ linearly with Lumi recalculate <BR>
at best ~3×10-8 at 90% CL
BsProspects
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 38
Kane, Kolda, Lannon hep-ph/0310042
MSSM• It is possible to constrain mA or/and tangiven an observation of Bs
•using BR(Bs)~ tan6/mA4
•Given Minimal Flavor Violation ↔ flavor change from CKM only•Substantial enhancement is possible in non-MFV case
Dedes, Huffman PLB600 (2004) 261
tan=50MFV
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 39
• Bs is a powerful probe of new physics. Could potentially provide the first hint of SUSY at the Tevatron• Using 364 pb-1 of data, CDF has obtained world best limits on Bs and Bd channels (submitted to PRL):
Br(Bs) < 1.6×10-7 @ 90% CL < 2.1×10-7 @ 95% CL
Br(Bd) < 4.2×10-8 @ 90% CL < 5.5×10-8 @ 95% CL
• The limits are now starting to constrain interesting regions of SUSY parameter space• An order of magnitude has been covered since Run I result. Will cover at least another order of magnitude before the end of RunII Hint of SUSY may just be around the corner!!
Summary
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 40
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 41
Backup Slides
BACKUP SLIDES
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 42
1) OS- : opposite-charge dimuon, < 02) SS+ : same-charge dimuon, > 03) SS- : same-charge dimuon, < 04) FM+: fake muon sample (at least one muon failed quality cut)
LH CMU-CMU CMU-CMX cut pred obsv pred obsv
OS- >0.90 37±1 32 33±1 36 >0.99 2.8±0.2 2 3.6±0.2 3
SS+ >0.90 0.25±0.03 0 0.44±0.04 0 >0.99 <0.10 0 <0.10 0
SS- >0.90 0.35±0.03 0 0.63±0.06 0 >0.99 <0.10 0 <0.10 0
FM+ >0.90 14.2±0.4 10 3.9±0.2 3 >0.99 1.0±0.1 2 0.41±0.03 0
Check Bgd Estimate Using Control Samples
Predictions are consistent with observations
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 43
For CMU-CMU:
• MC reproduces Data (LH>x) to 6% or better
After correction MC MC+0.01
• Assign 6% (relative) systematic
For CMU-CMX MC vs Data agreement is better
•No correction to MC is needed
Compare B+ Data and MCCheck MC Modeling of Signal LH
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 44
• CDF-D0 working group is formed to combine the B limits from both experiments: D0 Preliminary : Br(Bs) < 3.0×10-7 @ 90% CL (D0 note 4733, ~300pb-1)
CDF Preliminary : Br(Bs) < 1.6×10-7 @ 90% CL
• Two independent groups cross-checking each other’s combined results. Aim to release preliminary combined results for LP05
• Combined CDF and D0 results is expected to improve the limit by ~20%
CDF+D0 combination
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 45
CDF Run2.
s=1.96TeV σ(Inelastic)~60mb. ℒ ~71031cm-2s-1 (~400pb-1 good recorded)Plan: ~81031cm-2s-1 (Run2a); ~21032cm-2s-1 (4-8/fb Run 2)
1.7MHz collision20kHz L1 trigger350Hz L260Hz L3/logging rate. ~80% L1 (~1/3 at L3) of the trigger (bandwidth) are B physics
Better silicon coverage (2), muon detection, improved tracking.Better triggers: lower track pT, higher efficiency.
Run2 vs Run1
SVX II (5layer) silicon strip det svx+IP~40m
COT tracker drift chamber pT/pT
2~0.1%pT/pT
2~1.5%(L1/XFT)
CMU muon det (drift cham) pT>1.5GeV |
CMP muon det (drift cham + scint) pT>2.5GeV |
2 ft steel
2 ft steel
CMX muon det (drift cham + scint) pT>2GeV 0.6<|
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 46
Triggers used
Dimuon trigger pT>1.5GeV, pT>2GeV, 0.6<1pT, , muon ID used to cut on tracksUsed for X)
Two Track TriggerpT>2GeV, pT, , d0 info used to cut on 2 tracksUsed for: B,Dhadrons ; D
All are input to the various Level-3 triggersThat use the offline quality information
primary vertex
secondary vertex
impact parameter
~ 1 mmb, c decays
Semileptonic trigger pT, , d0, muon ID used to cut on tracksUsed for ,D,X)no results presented in this talk
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 47
Triggers usedDimuon trigger
pT>1.5GeV, pT>2GeV, 0.6<1pT, , muon ID used to cut on tracksUsed for X)
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 48
Triggers usedTwo Track Trigger
pT>2GeV, pT, , d0 info used to cut on 2 tracks @L2Used for: B,Dhadrons ; D
primary vertex
secondary vertex
impact parameter
~ 1 mmb, c decays
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 49
Br(Bs(d)μ+μ-) measurement.
Expect to detect at most few events that might only look like Bs(d)μ+μ–
SM predicts 0 events really a “search”Don’t look at the data signal region (blind search)Signal inside 5.169<MGeV/c2 (3window
demonstrate understanding of background events accurately estimate (acceptance) and
(efficiency) intelligently optimize cuts
Ldt
nnNμμ)BR(B
Bstotal
bgobsCLs 2
),(CL=90% upper limit on <nsig> for nobs
and nbg 171pb-1 or 10 trillion collisions
only Run1 Bs=0.9b for pTs>6 GeV/c, |y|<1
(use this as a baseline selection)3% (CMU&CMP Run1)
25% Run1 Dimuon trigger and pT>6GeVbaseline sample: 2940 events
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 50
Optimization ResultsOptimize on (M, c, , Iso) to get the best expected limit
(c,,Iso) =
(>200 mm, <0.10 rad, >0.65)
and mass window 80 MeV around
world avg Bs(d): 5.369 GeV (5.279 GeV)Bs(d): total = (2.0 0.2)%
(6.6%, total30%)Accepted bgd = (6 2) fb
Expected bacground
<Bgd> in 171pb-1 = 1.1 0.3 events
Ldt
nnPnnNμμ)BR(B
Bstotal
n bgbgs 2
)|()|( Poisson prob
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 51
R. Arnowitt et al.,hep-ph/0203069, PLB 538 (2002) 121mH
Overlap with measured δaμ (BNL)
in mSUGRA parameter space.
Overlap with dark matter=LSP allowed region.
Eliminate large parameter space (~ all for tanβ>40), with Br(Bsμ+μ-)~10-8 in Run2 (15/fb)
Motivations: Bsμ+μ- (mSUGRA)
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 52
_
’i23 i22
b
s
c b l s
l
R. Arnowitt et al.,hep-ph/0203069, PLB 538 (2002) 121
15 fb1
2 fb1
e.g., WTRPV = ijkLiLjEk ’ijkLiQjDk ’’ijkUiDjDk
RP Violation: Br vs. m1/2
12/20/04 Seminar FNAL
V. Krutelyov Search for SUSY using Bs 53
• CDF PRL 93, 032001, 2004 (171pb-1) Expected 1.1 background Observed 1 event
2004 CDF limit BR(Bs+-)
< 5.8 × 10-7 @90% CL < 7.5 × 10-7 @95% CL•Prior to that:
•CDF[94-97] (pub 2001) <2.0×10-6 @90% CL•UA1[84-89] (pub 1991) <2.5×10-5 @90% CL
• This analysis vs CDF2004:- Using ×2 data sample- Using extended muon coverage (increased acceptance by 50%)- Lowered pT threshold on B candidate- Improve signal bgd separation using a likelihood discriminant- Significantly improved the sensitivity of the analysis
Bsa Brief History