b s oscillations and rare decays at the tevatron
DESCRIPTION
B s Oscillations and Rare Decays at the Tevatron. GDR SUSY Workshop 28. April 2008 Strasbourg. Outline. Motivation Measurement of Bs mixing: m s Measurement of DG CP Violation in the B s system Rare leptonic decays b->llX transitions Summary. Motivation. Why huge - PowerPoint PPT PresentationTRANSCRIPT
1
Ralf BernhardUniversity of Freiburg
Ralf BernhardUniversity of Freiburg
28. April 2008 Ralf Bernhard
GDR SUSY Workshop28. April 2008 Strasbourg
Bs Oscillations and Rare Decays at the Tevatron
Bs Oscillations and Rare Decays at the Tevatron
2
Outline
Motivation Measurement of Bs
mixing: ms
Measurement of CP Violation in the Bs
system Rare leptonic decays b->llX transitions Summary
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Motivation
Why B Physics? - It’s got it all! Electroweak symmetry breaking determines
flavor structure: CKM matrix, CP violation, FCNC’s QCD Modeling: production, spectroscopy, masses,
lifetimes, decays Challenges lattice gauge, Heavy Quark Effective Theory, strong symmetries
Search for new physics rare decays and
Why at the Tevatron?
Complementary to (4S) B factories
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Why huge matter-antimatter
asymmetryin the universe?
Why huge matter-antimatter
asymmetryin the universe?
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Tevatron
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Tevatron continues to perform well Over 3.9fb-1 delivered and 3.4fb-1
recorded by each experiment, 2.8fb-1 analysed
Peak luminosities of ~3 x1032 cm-2 s-1 up to 10 interactions
5
Detectors
Relevant for B physics:DØ Tracker: excellent coverage
& vertexingSilicon & scintillating fiber Small radii, but extending to || < 2 New Layer 0 silicon on beam pipe in 2006, improving impact para. resol. Triggered muon coverage: || < 2 E.g.triggers: dimuons, single muons, track displacement @ L2
CDF Tracker: excellent mass resolution & vertexingSilicon, Layer 00Large radii drift chamber, many hits, excellent momentum resolutiondE/dx (and TOF): particle idTriggered muon coverage: || < 1E.g.triggers: dimuons, lepton + displ. track, two displaced tracks
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Mixing and Oscillations
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Mixing and Oscillations
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Mixing and Oscillations
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Whole new window for New physics
Very sensitive for NP
Sensitive for NP
Not sensitive for NP
Probe entire matrix
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Frequency of Oscillations
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Decays:
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Decay channels
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CDF Signal Selection
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DØ Signal Selection
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RunIIa
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Only 250 reconstructed and tagged hadronic events (CDF ~500)
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Decay channels
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Amplitude scan
tmAAPtmmP sss ±≈⇒±≈ cos1)(cos1)(
1/m
m
time
frequency
Asymmetry
Power spectrum
Motivation is to simplify combining results with other
experiments
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Bs: ms, Frequency of Osci.
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CP Violation
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In the SM CP violation occurs in only one place: complex phases in unitary CKM matrix; NP, plenty of places!!!
e.g. 43 in MSSM e.g. 43 in MSSM
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CP Violation
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In the SM CP violation occurs in only one place: complex phases in unitary CKM matrix; NP, plenty of places!!!
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CP Violation
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In the SM CP violation occurs in only one place: complex phases in unitary CKM matrix; NP, plenty of places!!!
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Bs: ms, Frequency of Osci
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TevtronB Factories
Not much room for New Physics!
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First assume no CP violation in Bs mixing,
s=0
First assume no CP violation in Bs mixing,
s=0
Measurement of Bs→Ds
(*)Ds(*)
Three channels [DsDs (PP), Ds*Ds (VP), Ds*Ds* (VV)]
Heavy quark limit + factorization Bs
odd→Ds*Ds is forbidden
Ds*Ds* in S-wave Ds(*)Ds(*) pure CP even
Flavor specific Bs lifetime Flavor specific decays carry equal amounts of BH and BL
Get flavor specific lifetime if FS data with is fit w/ single exponential
Bs→J/ P → VV Even and odd paths distinguishable with angular analysis of final
state particles
⎟⎟⎠
⎞⎜⎜⎝
⎛⎟⎠
⎞⎜⎝
⎛
Ο+⎟⎠
⎞⎜⎝
⎛
=→ 1
2)( (*)(*) CP
sss DDBBF
CP and mass eigenstates are the same
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from Bs→Ds(*)Ds
(*)
Trigger on muon from semileptonic Ds decay Ignore any photons Look for correlated production of Ds→and Ds→
Bs Ds
Ds
1
Phy
. Rev
.Let
ters
99,
241
801
(200
7)
22
from Bs→Ds(*)Ds
(*)
Bs Ds
Ds
1
031.0038.0030.0035.0
016.0019.0015.0017.0
(*)(*)
079.0
039.0)(
++−−
++−−
=
=→
CP
sss DDBBF
Phy
. Rev
.Let
ters
99,
241
801
(200
7)
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Bs Flavor Specific Lifetime
psBsFS052.0046.0055.0381.1)( +
−±=τ
Phy
s.R
ev.L
ett.
97:2
418
01,2
006
Ds→D+→
hep-
ph/0
2010
71
Know flavor at time of decay from charge of decay product
50% CP-even, 50% CP-odd at time t0
+-
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Bs Flavor Specific Lifetime
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Bs→J/
Heavy (H, CP-odd) and Light (L, CP-even) Bs states
Decays into two vector mesons that areeither CP-odd (L=1) or CP-even (L=0,2)
Time-dependent angular distributions allow separation of components
Simultaneous fit to lifetime and three angles
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Not “flavor specific”,predicted to be moreCP even than odd
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Bs→J/
odd / heavy
even / light
1976±65 Candidate BS
arXiv:/0802.2255
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arXiv:/:0712.2348
2506±51
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and s
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First assume no CP violation in Bs mixing,
s=0
First assume no CP violation in Bs mixing,
s=0CP and mass eigenstates are the same
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CP Violation
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In the SM CP violation occurs in only one place: complex phases in unitary CKM matrix; NP, plenty of places!!!
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CP Violation in Bs System
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In the SM CP violation occurs in only one place: complex phases in unitary CKM matrix; NP, plenty of places!!!
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Explore new part of matrixExplore new part of matrix
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CP Violation in Bs System
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In the SM CP violation occurs in only one place: complex phases in unitary CKM matrix; NP, plenty of places!!!
Explore new part of matrixExplore new part of matrix
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CP Violation in Bs System
How could New Physics affect these phases
Both CDF and DØ measure/observe the phase responsible for CP violation in Bs -> J/ decays
Use flavor tagging to identify initial flavor of Bs or Anti Bs in J/ decays (and know value of ms)
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CP Violation in Bs→J/ Even without initial state flavor tagging, have
sensitivity to s
But 4-fold ambiguity, reduce to 2-fold with flavor tagging...
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CP Violation in Bs→J/
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Now use initial state flavor tagging
Ambiguities
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CP Violation in Bs→J/
Now using initial state flavor tagging, constrain strong phases
Ambiguities
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s Measurement
In Standard Model: s≈arg(-Vts) ≈ 0.004 rad.In Standard Model: s≈arg(-Vts) ≈ 0.004 rad.
Observables: Semileptonic asymmetries, interference in decays to CP eigenstates
A. L
enz,
U. N
iers
te h
ep-p
h/06
1216
7
Bs
Ds
Bs
Bs
Ds
Bs
B
B ↕ this versus this ↕
Two samples
Exclusive untagged Ds
Inclusive like-sign
φ
tan)()()(
)()(
muntaggedA
DNDN
DNDNSL
ss
ss
Δ
ΔΓ≈=
+
−−+
−+
φ
tan)()()(
)()(
muntaggedA
DNDN
DNDNSL
ss
ss
Δ
ΔΓ≈=
+
−−+
−+
)(2)()()(
)()(untaggedAtaggedA
NN
NNSLSL ==
+−
−−++
−−++
)(2)()()(
)()(untaggedAtaggedA
NN
NNSLSL ==
+−
−−++
−−++
36
Same sign Dimuons
0032.00044.00092.0 ±±−=SLA
)()( sSLdd
ssdSLSL BA
Zf
ZfBAA +=
N(same sign) ≈ 310K
0101.00064.0),( ±−=sSL BA
Z ~ 2
Phy
s. R
ev. D
74,
092
001
(200
6)
~60/40 mix of Bd and Bs
ASL(Bd)=-0.0047±0.0046 (HFAG, B-factories )
)(2)()()(
)()(untaggedAtaggedA
NN
NNSLSL ==
+−
−−++
−−++
Regular flipping of polarity of solenoid (tracking) and toroid (muons) magnets essential for controlling systematic uncertainties
37
Exclusive Bs→Ds±Results
€
ASL (Bs,Dsμ) =
0.0245 ± 0.0193± 0.0035
€
ASL (Bs,Dsμ) =
0.0245 ± 0.0193± 0.0035
0090.00001.0
),(
±=+ ssSL DBA
0090.00001.0
),(
±=+ ssSL DBA
Exclusive Ds
m()
pol
pol
DØ Combined:
116.002.0tan −±=⋅ psss φUsing ms from CDF:
Phy
s. R
ev. L
ett.
98, 1
5180
1 (2
007)
φ
tan)()()(
)()(
muntaggedA
DNDN
DNDNSL
ss
ss
Δ
ΔΓ≈=
+
−−+
−+
φ
tan)()()(
)()(
muntaggedA
DNDN
DNDNSL
ss
ss
Δ
ΔΓ≈=
+
−−+
−+
CDF: 1.6 fb-1, CDF Note 9015CDF: 1.6 fb-1, CDF Note 9015QuickTime™ and a
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s Results
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Combined with older DØ analysis before flavor tagging
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CP Violation in Bs: Combination
In Bs→J/ flavor-tagged analyses, in (s,s) space CDF has ~1.5 deviation from SM, DØ ~1.8 deviation, consistent with each other
Need to be careful, non-parabolic log(L), multiple correlations (best is simply more data!!)
DØ, 2.8fb-1
40
UTfit results
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Next talk from Marcella Bona
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Direct CP violation in b Hadrons
Direct (not through mixing) CP violation expected to be large in some b hadron decays, including B mesons and b Baryons
Measure asymmetry: f=final state
CDF: Br's and asymmetries of two-body charmless states, Bhh’
Expectations, asymmetry ~30% First CP asymmetry measurement
in b baryon decays
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Direct CP violation in b Hadrons
DØ: Small (~1%) CP asymmetry expected in SM for B+→J/K+
Again, frequent solenoid and toroid polarity reversals essential to control charge asymmetry systematic uncertainties
Correct for K+/K- asymmetry <1% precision factor ~2
better than current world average
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Accepted by Phys. Rev. Lett.
43
Purely leptonic B decay
B->l+ l- decay is helicity suppressed FCNC SM: BR(Bs->) ~ 3.410-9
depends only on one SM operator in effective Hamiltonian, hadronic uncertainties small
Bd relative to Bs suppressed by |Vtd/Vts|2 ~ 0.04 if no additional sources of flavor violation
reaching SM sensitivity: present limit for Bs -> +- comes closest to SM value
SM expectations: Current published limits at 95%CL:
Br(Bdl+l-) Br(Bsl+l-)
l = e 3.4 × 10-15 8.0 × 10-14
l=μ 1.0 × 10-10 3.4 × 10-9
l=τ 3.1 × 10-8 7.4 × 10-7
Br(Bdl+l-) Br(Bsl+l-)
l = e < 6.1 ·10-8 < 5.4 ·10-5
l=μ < 1.8 ·10-8 <5.8 x 10-8
l=τ < 2.5% < 5.0%
44
Purely leptonic B decay excellent probe for many new
physics models particularly sensitive to models
w/ extended Higgs sector BR grows ~tan6 in MSSM 2HDM models ~ tan4 mSUGRA: BR enhancement
correlated with shift of (g-2)
also, testing ground for minimal SO(10) GUT models Rp violating models,
contributions at tree level (neutralino) dark matter …
Two-Higgs Doublet models:Two-Higgs Doublet models:
Rp violating:Rp violating:
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Search Strategy
Preselection of Di Muon events Normalization channel B+→J/ψK+
Background estimation using sidebands
Background reduction using a LHR (DØ) or NN (CDF)
0.8 ± 0.2 eventsObserve 1 event
NN
RunIIa
46
Limits
Relative NormalizationB+ /Bs relative efficiency of normalization to signal channelfs/fu fragmentation ratio - use world average (3.71) with 15%
uncertaintyBd /Bs relative efficiency for Bd-> versus Bs-> events in
Bs search channel (~0.95) R = BR(Bd)/BR(Bs) is small due to |Vtd/Vts|^2
Br(Bs-> 2 fb-1 7.3×10-8 Prelim.DØ
Br(Bs-> 2 fb-1 4.7×10-7 Prelim.CDF
Br(Bs-> combined 3.6×10-8 HFAG
at 90% CL
DØ Note 5344
PRL 100,101802 (2008)
47
Rare decays constraining NP
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Study of b -> s l+l-
long-term goal: investigate b -> s l+ l- FCNC transitions in B+, Bd and Bs mesons
B+ -> l+ l- K+ and Bd -> l+ l- K* established at B factories Bs -> l+ l- only accessible at the Tevatron
SM prediction: short distance BR: ~1.6×10-6 About 30% uncertainty due to B-> form factor
2HDM: enhancement possible, depending on parameters for tan and MH+
49
b->sl+l- Theory
The forward backward asymmetry
is defined as the asymmetry between
forward and backward emitted
positive leptons in the dilepton rest frame
where the direction is relative to the
direction of the B meson.
The forward backward asymmetry
is defined as the asymmetry between
forward and backward emitted
positive leptons in the dilepton rest frame
where the direction is relative to the
direction of the B meson.
Mass spectrum Mass spectrum
Sensitive to “newPhysics” contribution
50
B->h @ CDF
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arXiv:0804.3908
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Branching ratio overview
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Need more statistics to measure charge asymmetry vs. invariant di-lepton mass and to add Bs channel! Need more statistics to measure charge asymmetry vs. invariant di-lepton mass and to add Bs channel!
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Summary
ms established and well measured at the Tevatron
Bs system and CP studies opening a powerful new window: possibly already providing hints of new phenomena?
Limit on rare decay Bs->is getting more and more stringent, help constrain physics beyond the SM
Other FCNC (b-> sll) decays test the SMTevatron doing very well, expect to at
least double our data-set by the end of running
53
Back up slides
54
Pre-Selection
Cut on Mass region of di-muon sample 4.5 < m < 7 GeV/c2
Two medium muons with a net charge of zero and a pT greater than 2.5 GeV
The triggered muons have reconstructed tracks in the tracker with at least 3 hits in the Silicon tracker at least 4 hits in the Fiber tracker
Good reconstructed vertex (cut) Cut on the uncertainty of the transverse decay
length (Lxy) < 150 m A minimum pT of the Bs candidate of 5 GeV is
required
55
Normalization
Additional cuts on the Kaon and B candidate are: Kaon pT > 0.9 GeV/c Collinearity of > 0.9 is required 2 of the vertex fit contribution not more than 10, together < 20 Also cut on the LHR cut like the Bs->signal
56
Likelihood
RunIIa
RunIIb
57
Systematic Uncertainties
58
Bs→J/
Time evolution: even plus odd components
t
t
oddeven
H
L
eoddtf
eeventf
CPCAA
tAtAt
−
−
≈
≈
+
+≈
),(
),(
)(
),,,(),,,()(*
θθCP conserving interference
CP states = heavy, light states
Time evolution: pure even case
t
even
Leeventf
tAt−≈
≈
),(
),,,()( θ
59
ts
ts
ts
ts
stt
oddeven
LH
HL
HL
eeoddtf
eeeventf
eeCPVAA
CPCAA
tAtAt
−−
−−
−−
−++≈
−++≈
−+
+
+≈
)cos1()cos1(),(
)cos1()cos1(),(
sin))((
)(
),,,(),,,()(
*
*
φφ
φφ
φ
θθ
Bs→J/
Time evolution: even plus odd plus CPV
CP conserving interference
Heavy and light states are mixed CP
CP violating interference between two paths
Time dependent angular analysis of untagged sample
60
Combined (coss≡1)
61
Bs→J/Results
(ps-1)
τ(ps)
(ps-1)
s(rad)
log(L) = 1
Likelihood invariant to simultaneous flip of sign of
and even-odd strong phase difference 4-fold ambiguity
14.001.0
1
56.079.0
02.009.017.0+−
−
±−=
±±=
s
s ps
φ
Phy
s. R
ev. L
ett.
98, 1
2180
1 (2
007)
62
Bs→J/ angles
63
Flavor Specific Bs Lifetime
( )LHss BBDB +=→2
1μν
( )LHFS ttt eee τττ ///
2
1 −−− +≡
Flavor specific decays carry equal amounts of BH and BL
Get the flavor specific lifetime when you fit FS data with single
exponential
Maps out a 2-D constraint on the average width and the width
difference
=
⎟⎟⎠
⎞⎜⎜⎝
⎛
−+
=
2
1
112
2
y
y
y
sFSτ
hep-ph/0201071
64
Bs Semileptonic Sample
Ds→D+→
+
K+
KBs Candidate
SVPV
Charge correlation to isolate Bs sample
Transverse decay length determined in lab frame
Boost back using MC to estimate neutrino momentum
65
Bs→J/ P →VV
Even and odd paths distinguishable with angular analysis of final state particles
A0 A||
Even waves
A┴
Odd waves
Proper time
66
Bs→J/
1039±45 Bs Candidates
Flight length significance > 5