Experimental proposal for MDM/EDM of strange baryons in LHCb
cLFV & BNV - CERNcds.cern.ch/record/2280092/files/Onderwater.pdfcLFV & BNV Searches @ LHCb Gerco...
Transcript of cLFV & BNV - CERNcds.cern.ch/record/2280092/files/Onderwater.pdfcLFV & BNV Searches @ LHCb Gerco...
cLFV & BNVSearches @ LHCb
Gerco Onderwateron behalf of the LHCb collaboration
Flavour2017, Qui Nhơn, Việt Nam, 13-19 August 2017
Outline
LHCb Experiment
LFV with muons : τ→μμμ
LFV with electrons : D0→eμ
LFV with taus?
BNV & LNV
Conclusion
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τ
μ
B+
π
ντπ
πK+
LHCb
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LHCb : precision measurement
Triggerhigh efficiency esp. muon triggers
Int. J. Mod. Phys. A 30, 1530022 (2015)
Muon IDidentification ε ~ 97% misID ~ 2%
RICHPID ε(K) ~ 95% for MisID(π→K) ~ 5%
VELO IP resolution 15+29/(pT/GeV) μm
Tracking Δp/p0.4% @ 5 GeV/c – 1.0% @ 200 GeV/c
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Recent LHCb results
D0 → eμ PLB 754 (2016) 167 LFV
B0 → D*+ τντ / μνμ PRL 115, 111803 (2015) LNU Julian
τ → μμμ JHEP 02 (2015) 121 LFV
B+ → K+μμ / ee PRL 113, 151601 (2014) LNU Julian
B– → π+μ–μ– PRL 112, 131802 (2014) LNV
τ– → pμ–μ– PLB 724 (2013) 36 BLNV
D+ → π–μ+μ+ PLB 724 (2013) 203 LNV
B0 → eμ PRL 111 (2013) 141801 LFV
(s)
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μ detection
μ
μ
μ
τ
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Challenge : τ decays at hadron collider
B factory
✘ Babar & Belle ~3x109 τ-pairs
✓ e+e‒ → τ+τ‒ extremely clean
✓ tag with opposite τ possible
LHC
✓ LHCb ~3.5x1011 τ's in detector acceptance in 2011 & 2012
✘ Nearly no direct τ production, mainly from Ds decay
✘ No “production traces” in Ds → τντ
✘ Charm decay with missing particles similar to τ signature
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τ → 3μ search
Approach:■ trigger on muon and secondary vertex■ multivariate analysis to discriminate signal and background■ control sample for normalization and calibration
μ
μ
μ
τ
Dsprimary vertex
secondary vertex
ν
main tauproduction viadecay of Ds
JHEP 02 (2015) 121
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Signal candidate selection
Trigger■ muons not “in beampipe” (pT > 1.48 GeV/c)■ two-, three- or four-track secondary vertex■ at least one particle does not point to collision point
Analysis■ no tracks may point to collision point■ good 3-track vertex■ decay-time compatible with τ decay (ct > 100 μm)■ τ momentum must point back to PV
Background elimination■ |M(μ+μ‒)−M(Φ)| > 20 MeV/c² Ds‒ → Φ(μ+μ‒)π‒
■ M(μ+μ‒) > 450 MeV/c² Ds‒ → η(μ+μ‒γ)μ‒νμ■ M(μ‒μ‒) > 250 MeV/c² reconstructed from same particle
JHEP 02 (2015) 121
misID
missing mis-reconstructed
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Signal & background discrimination
Three likelihoods to distinguish signal from background
I. L3body : decay topology
II. LPID : μ identification
III.L3μ : tau selection
L3body
LPID
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M3μ distribution
■ Shape determined using Ds‒ → Φ(μ+μ‒)π‒
■ Analyze 5x5 best bins in LPID and L3body
Blind analysis
LPID : [0.65, 1.0]L3body : [0.725, 1.0]
JHEP 02 (2015) 121
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M3μ distribution
Bkgd Signal Bkgd
■ Shape determined using Ds‒ → Φ(μ+μ‒)π‒
■ Analyze 5x5 best bins in LPID and L3body
LPID : [0.65, 1.0]L3body : [0.725, 1.0]
JHEP 02 (2015) 121
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dashed : expected solid : observed
68%
95%
Result
– Robust analysis method – Statistics limited – No significant evidence for excess of events
B(τ‒ → μ‒μ+μ‒) < 4.6 x 10-8
@ 90% C.L.
Belle 2.1 x 10-8 @ 90% C.L.
BaBar 3.3 x 10-8 @ 90% C.L.
@Run2: LHCb may overtake Belle… which will then be overtaken by Belle-II
JHEP 02 (2015) 121
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e detectione
μ
D0
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D0 → eμ
e
μ
D0
D*+
π+
Belle : Br(D0 → eμ) < 2.6x10–7 (90% CL)
RPV SUSY : ~10–7 Leptoquarks : 4x10–8
LHCb analysis based on 3 fb–1 collected @ √s = 7 & 8 TeV
D*+ → D0 π+
↳ D0 → eμ Signal ↳ D0 → K– π+ Normalization
PLB 754 (2016) 167
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Bremsstrahlung
e → eγ
also study w/B+ → J/ψ K+
↳e+e–
PLB 754 (2016) 167
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Mis-Identification
Probability forπ+π– → eμ mis-ID~ (1–2)x10–8
Kπ
π+π–
PLB 754 (2016) 167
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Unbinned simultaneous fits
BKGD-like
intermediate
Signal-like
-7±15 events
m(eμπ)-m(eμ) → MD*-MDm(eμ) → MD
Signal + bkgd
D0→eμ (signal)
PLB 754 (2016) 167
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dashed : expected solid : observed
Result
–Robust analysis method –Statistics limited –No significant evidence for excess of events
B(D0 → eμ) < 1.3 x 10-8
@ 90% C.L.
20x improvement over previous resultEffectively deal with backgroundsBremsstrahlung complicates analysis
PLB 754 (2016) 167
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Other channels under investigation
B(s) → eμ
B0 → K*0eμ
Bs → Φeμ
B(s) → J/Ψ(→eμ) X
B+ → K+eμ
Expect to improveexisting limits
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τ detectionOpportunities for
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Some existing limits
J/ψ(1S) → μτ < 2x10–6
Υ(1S) → μτ < 6x10–6
Υ(2S) → μτ < 3x10–6
Υ(3S) → μτ < 3x10–6
Z0 → μτ < 1x10–5
h0 → μτ < 1.5%
J/ψ(1S) → eτ < 9x10–6
Z0 → eτ < 1x10–6
O(few x 10-6)@ 90-95% CL
Particle Data Group
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Reconstruction – I
Interesting possibilityShort lifetime prohibits direct detection
τ
μ
B0
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Reconstruction – II
τ
μ
B0
μ
νμ
ντ
Interesting possibilityShort lifetime prohibits direct detectionNeutrinos remain undetected
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Reconstruction – III
τ
μ
B0
π
ντπ
π
Interesting possibilityShort lifetime prohibits direct detectionNeutrino remains undetected Br ~ 9%
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Reconstruction – IV
τ
μ
B+
π
ντπ
πK+
Interesting possibilityShort lifetime prohibits direct detectionNeutrino remains undetected
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Reconstruction – V
τ
μ
π
ντπ
π
Interesting possibilityShort lifetime prohibits direct detectionNeutrino remains undetected
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Possibly interesting channels
B(s) → e/μτ
B+ → K+e/μτ
Υ(nS) → e/μτ
Benefit from B0 → D*+τντ & B(s) → ττ
τ
μ
π
ντπ
π
τ
μ
B+
π
ντπ
πK+
τ
μ
B0
π
ντπ
π
Phys. Rev. Lett. 115, 111803 (2015)Phys. Rev. Lett. 118, 251802 (2017)
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BNV & LNV
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LHCb LNV & BNV results
B– → D*+ μ– μ– < 2.4x10–6
→ D0π+ μ– μ– < 1.5x10–6
→ D+ μ– μ– < 6.9x10–7
→ Ds+ μ– μ– < 5.8x10–7
→ K+ μ– μ– < 5.4x10–8
→ π+ μ– μ– < 4.0x10–9
Ds–→ π+ μ– μ– < 1.4x10–7
D– → π+ μ– μ– < 2.5x10–8
τ– → pμ– μ– < 5.4x10–7 *
→ pμ+μ+ < 4.6x10–7
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Search for Majorana ν's
Best limits to date, stillto be improved
Note: B–L not conserved(except *)
PRL 112 (2014), 131802 PLB 724 (2013), 36PLB 724 (2013), 203 PRL 108 (2012), 101601
PRD 85 (2012), 112004
LNV / BNV / (B–L) conserving
D0 → p μ–
B0(s) → p μ–
B0(s) → Λc μ–
Λ0(b) → K+ μ–
Λ0b → D+(s) μ–
Λ+c → μ+μ+μ–
M0 → B+ ℓ– (0,0) → (+1,+1)B0 → M+ ℓ– (–1,0) → (0,+1)B+ → ℓ+ℓ+ℓ– (+1,0) → (0,–1)
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Bein
g in
vestig
ate
d
Conclusion
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Take away message
LHCb : diverse program studying flavor physics with all three quark & lepton generations
With LHC Run-I data LHCb sharpened limits for manyLFV, LNV, and BNV channels
No significant deviations from SM seen
Demonstrated sensitive BSM searches @ hadron collider
Many more options around, lots of additional dataexpected in Run-II & Run-III
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Thank you for your attention!
Gerco Onderwater, Flavour2017