Highlights from the LHCb Experiment
description
Transcript of Highlights from the LHCb Experiment
UFRJ
Highlights from the LHCb Experiment
SILAFAE 2012
Kazu AkibaUFRJ-Brazil
On Behalf of the LHCb Collaboration
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ContentsB physics at the LHC.The LHCb Experiment.LHCb physics results
Bs->μ+μ γ from B->DK B->hhh D mixing pA Run TOO MANY!!!(82 papers submitted, over 100 conference notes ) List: http://cdsweb.cern.ch/collection/LHCb%20Papers?ln=en
The UpgradeConclusionNot Covered: Posters!
BJ/ΨKs decays -- Daniela Szilard Le Cocq D'Oliveira The LHCb’s Jet Reconstruction -- Oscar A. A. Francisco Electroweak studies at LHCb -- Valdir S. Guimaraes
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B Physics at the LHC
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π+Bs0
μ-
Ds-
Beam 2Beam 1
PV
IP
A hadron collider provides many B particles to study:
High b and c production cross section at the TeV scales.
Also provides B and D particles with a high boost. Long lived particles can be distinguished from the prompt ones.
Production at low angles…But also high background rateRequirements:
Good vertex, IP resolution. Good particle identification. Highly selective trigger
bb production along the beam axis.
_
σ(pp→bbX) = 75 ± 14 μb *
* Phys. Lett. B 694 (2010) 209
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The LHCb Experiment
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Large Hadron Collider beauty Experiment for CP violation and Rare B Decays.
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The LHCb Experiment
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TTSi
Muon
MWPCGEM
HCAL
ECAL RICH2 Outer Tracke
r straw Tubes
Magnet
RICH1
VELO&PUSi
Inner Tracke
r Si
+ TriggerHard &
Soft
Large Hadron Collider beauty Experiment for CP violation and Rare B Decays.
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The LHCb Experiment
Kazu Akiba SILAFAE 12.12.12
TTSi
Muon
MWPCGEM
HCAL
ECAL RICH2 Outer Tracke
r straw Tubes
Magnet
RICH1
VELO&PUSi
Inner Tracke
r Si
+ TriggerHard &
Soft
Zoom in the vertex
region
Closes for
physics
Open during
injection
Large Hadron Collider beauty Experiment for CP violation and Rare B Decays.
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The LHCb Experiment
Large Hadron Collider beauty Experiment for CP violation and Rare B Decays.
μ
K, π
n
γ
e-
pp
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LHCb in Numbers
Great Vertex Resolution! Primary/secondary separation, proper time resolution.
Excellent momentum and mass resolution.Outstanding PID (K-π) and μ reconstruction.Dedicated Trigger system for B and C!
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Operations
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High Efficiency!
Over 2/fb acquired this year! More than 3/fb integrated
Operating at 4x the designLuminosity / bunch
All to provide MANY physics results…(Most of results presented here with 2011 Data alone)
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Bs μ+μ-
Very small branching ratio, but very well predicted in the Standard model: (3.54±0.30) x 10-9
But possibly enhanced by new physics:
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SM NP
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Bs μ+μ- AnalysisA multivariate analysis strategy using a BDT method to discriminate signal/background.
main background bb->μ+μ-X special care with Bhh’ (h(‘)μ)Peaking backgrounds well modelled.
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Bs μ+μ-
EvidenceBR(Bs μ+μ-) = (3.2-
1.2+1.5 )x10-9
3.5 s excessCompatible with standard
model2011 + ½ 2012 (2.1/fb)1/fb left to be analysed.LHCb-PAPER-2012-043
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UFRJ14Kazu Akiba
Approaching γThe least precisely measured angle in the CKM
unitarity triangles: B factories σ ~15-16o (see CKM2012 WG:V )
Direct measurements require the observation of very suppressed channels (Vub)
It requires the delicate observation of interference
LHCb has the capability ofmeasuring γ in a wide varietyof channels with contributionsfrom tree diagrams or penguin.
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BDK
BDK family provides a theoretically clean lab to measure γ.
Several different observables f provide independent measurements .
The increasing statistics of LHCb will populate the suppressed decays required for an over constrained measurement of γ.Kazu Akiba SILAFAE 12.12.12
Where f can be: Kπ, KK, ππ, Kπππ, Ksππ, KsKK, Kππ0 …
→ f
→ f
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B0D0K0*First observations of very suppressed channel!2011 dataset (LHCB-CONF-2012-024)
Shows already some CP violation.Asymmetry A (KK) = -0.47 +0.24
-0.25 ±0.02 (sys)
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B+D0K+
Combination of the ADS/GLW and GGSZ (Dalitz) give the LHCb’s constraint on γ = (71 +16
-15 )o
(CERN-LHCb-CONF-2012-032)
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B+ DK+ , with D hh [GLW/ADS*] PLB 712 (2012) 203B+ Dπ+ , with D hh [GLW/ADS] PLB 712 (2012) 203B+ DK+ , with D Ks hh [GGSZ] arXiv 1209.5869B+ Dπ+ , with D Ks hh [GGSZ] arXiv 1209.5869B+ DK+ , with D πKππ [ADS*] LHCb-CONF-2012-30B+ Dπ+ , with D πKππ [ADS*] LHCb-CONF-2012-30B+ DK+ππ , with D hh [GLW*/ADS] LHCb-CONF-2012-21 B0 (s) DK*0 , with D hh [GLW/ADS] LHCb-CONF-2012-24B0 (s) DKK with D hh [GLW/ADS*] PRL 109 (2012) 131801* First observations
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BhhhDisclaimer: Charged B and charged h…Access to t → s,d (Penguin) and
the CKM phase γ b → u (Tree) interfering diagrams.
CP violation expected from interference between tree and penguin diagrams.
CP violation expected also from interferences between resonances in the phase space.
A complete analysis of the CP asymmetries in the phase space is needed for a complete understanding.
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ACP in BhhhMeasuring a a few combinations of final
states:B+Kππ , B+KKK , B+πππ , B+KKπLHCb-CONF-2012-018, LHCb-CONF-2012-028
Assymetries observed and well controlled using control channels (B J/Ψ K). ACP(Kππ) = 0.034 ± 0.012 ACP(KKK) = - 0.046 ± 0.012 ACP(πππ) = 0.120 ± 0.028 ACP(πKK) = - 0.153 ± 0.050
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UFRJ20Kazu Akiba
Bhhh DalitzStudy of CPV across Dalitz
plot (ACP vs m2hh):
large CPV in specific resonance areas
Typically at low m2 . More experimental work needed as well as on theory side
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Not only Beauty: Charm physics
More than just beauty in LHCb since the beginning!Production cross section of charm at the LHC energy
is very high. Indeed it’s kind of a background for the B trigger Charm trigger is limited by the trigger selection and bandwidth.
Small CP violation in the charm sector: any significant observation could be a sign for “new physics”.
Asymmetries in D0 decays seem to be a good place to look for it
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Time integrated ACP
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*To first order
*
A more robust measurement is given by
For a CP eigenstate final state (K-K+ or π+π-): pp collisions
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ΔACP measurement
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3.5 σ away from zero First evidence of CPV in the charm
sector
BUT: many other places to confirm it:
D+hhh, D0->hhhh, Ds , …
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Brief reminder of mixingTime Evolution of Schödinger’s equation:
Mass eigenstates can have different masses and decay widths than flavour states. Pure sample becomes mixed…
If CP is conserved, q/p = 1, and q and p are real (no phase)
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Charm MixingMixing in D0 should be very small in SM and therefore could be a
probe for NP… Small contributions from box diagrams b loop CKM suppressed (|VubV*
cb|2≪1) s, d loops GIM suppressed ( (m2
s-m2d)/m2
W~0) Long-distance effects important (and difficult to calculate)
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Very slow…
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Measuring mixing in charm
Start with a D*+D0π+ tagged sampleFit first clean RS sample and determine signal
shape Then fit WS sample with the signal shape fixed by
RS sample Calculate WS/RS ratio R, fit the ratio of yields vs
decay timeflat? no mixingnot flat? mixing
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Results
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x = Δm/Γ, y=ΔΓ/2Γ ; x’ = x cos δ + y sin δy' = y cos δ − x sin δ
No-mixing Hypothesis excluded at 9.1σarXiv:1211.1230
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Results
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No-mixing Hypothesis excluded at 9.1σarXiv:1211.1230
x = Δm/Γ, y=ΔΓ/2Γ ; x’ = x cos δ + y sin δy' = y cos δ − x sin δ
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Mixing in BsJ/ψφ : ϕsϕs is the CP violating phase difference between
oscillated and non-oscillated B0s decays.
In the SM ϕs is equal to 2βs = 2arg(-VtsV*tb/VcsV*
cb).
ϕsexpected
= 0.036 ± 0.002 rad
“New Physics” contributions to the box diagram could contribute a different value of ϕs …
With this channel ΔΓs and Γs
can be extracted from the Multi dimensional fit
A good sample of BsJ/ψφSILAFAE 12.12.12
2011 data
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Angular analysisBsJ/ψφ is a mixture of CP-even and odd final states
(V V) Need an angular analysis to disentangle, but that also provides
all the information we need.We also need a good proper time resolutionAnd B tagging…
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J/ψ rest frame Φ rest frame
2011 data
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Proton-IonSept 13th – pA run (also) in LHCb ~4 hour data taking at L ~
5 1025 cm-2s-1
Very good and stable conditionsNo problem of multiplicities in the detectorUse of the System for Measuring Overlap with GasKS ,Λ, , f D peaks reconstructed offlineGood expectations for January (pA, Ap) run
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Proton-Ion
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h
Sept 13th – pA run (also) in LHCb ~4 hour data taking at L ~ 5 1025 cm-2s-1
Very good and stable conditionsNo problem of multiplicities in the detectorUse of the System for Measuring Overlap with GasKS ,Λ, , f D peaks reconstructed offlineGood expectations for January (pA, Ap) run
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Proton-Ion
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Sept 13th – pA run (also) in LHCb ~4 hour data taking at L ~ 5 1025 cm-2s-1
Very good and stable conditionsNo problem of multiplicities in the detectorUse od the System for Measuring Overlap with GasKS ,Λ, , f D peaks reconstructed offlineGood expectations for January (pA, Ap) run
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Ks , L PRELIMINARY
l
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R =1.745 ± 0.014(stat)
R =1.818 ± 0.043(stat)
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Motivation
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Currently LHCb design can cope with Lumi./bunch L > 4Ldesign LHC still provides more than what we can handle:
Current detector is limited due to 1 MHz readout. Higher Luminosities do not translate to higher yields for hadronic modes.
The upgrade is planned as a major Trigger/Readout upgrade: From 1 to 40 MHz full readout Every collision read out to a computing farm Higher instantaneous Luminosity Higher occupancies Full tracking in the trigger
ATLAS/CMS
LHCb Plan to go to20 x 1032 cm-2s-1
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Detector Upgrade
VELO
Si Strips
(replace all)
Muon
MW
PC(almost
compatible)
Calo PMTs
(Reduce PMTs
gain+ replace R/O)
RICH HPDs(replace HPDs
+ R/O)
Silicon Trackers Si Strips (replace all)
Outer Trackers Straw tubes(replace R/O)
Option: Scint. Fibres
Design a common Read Out Board : Tell 40. SILAFAE 12.12.12
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Schedule
March 2011, “Letter of Intent for the LHCb Upgrade” submitted to LHCC
June 2011, LHCC endorses the LOI, green light for TDR preparation
June 2012, Submission of “Framework TDR for the LHCb Upgrade” to LHCC, endorsed in September/2012.
2013, R&D, technological choices, preparation of subsystems TDRs
Mid/end 2013, Submission of LHCb subsystems TDRs to LHCC
2014-2015, R&D of the choices and production of new detectors/ test of 40MHz prototypes.
2017-2018 Long Shutd. 2 / LHCb upgrade installation
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UFRJ44Kazu Akiba
ConclusionsThe LHCb has an outstanding performance!
Just a few of the achievements of the experiment. Mostly with 2011 dataset: 1/fb . Now:>3/fb!
First evidence of Bsμμ. First measurements of the CKM γ phase. Observation of very
suppressed channels Large CP asymmetry in B3 h; More analysis & theory needed! First evidence found CPV in D0 decays LHCb observed D0 mixing. No mixing excluded with 9.1σ. ϕs= -0.001 ±0.101(stat)±0.027(sys) ; no indications of NP. Nice data taking and analysis capability and in the pA run.
The results from the current experiment motivate for a complete Upgrade of the detector All the front end to be upgraded. Vertex/Tracking improvement. R&D effort coordinated up until 2016, installation in 2017.SILAFAE 12.12.12
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Rare Decays summary
D0 μ+μ- BR < 1.3 x 10-8 new world best limit
K0S μ+μ- BR < 11 x 10-9 new world
best limitB0
(s) μ+μ-μ+μ- BR < 1.3 (5.4)x10-8 first limits
B0 μ+μ- BR < 9.4x10-10 new world best limit
B0s μ+μ- BR = (3.2+1.5
-1.2)x10-9 first evidence!
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Combination of AΓ and ΔACP
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Mod. Phys. Lett. A, Vol. 27, No. 26 (2012) 1230026
CL for no CPV : 2x10-5
• Plenty of theoretical papers since the evidence for ΔACP≠0 • Values of the order of 10-2 seem possible due to enhanced penguin
amplitudes• Still , no clear picture on whether SM (enhanced penguins) or NP more
measurements
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Few examples
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Carbon
fibre
-sensor
R-side circuit
-sidecircuit
R-sensor