2014, Sept 9Accueil M2Julien Cogan

The LHCb experiment

julien.cogan@free.fr

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Triumph of the Standard Model

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Is it the end ?

Is it the end ? Certainly not !Open questions pointing towards the existence of physics beyond the SM :

Cosmological dark matter Baryon asymmetry of the Universe Non-zero (but small) neutrino

masses quark and lepton masses

hierarchical structure :

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Beyond the Standard Model ???

New degrees of freedom are expected at a scale Λ above the electroweak scale

Which is the energy scale of New Physics (or the value of Λ) ?

Which is the symmetry structure of the new degrees of freedom(or the structure of the cn) ?

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Two natural paths to look for new physics

Direct search (ATLAS & CMS)

production of new particles (real)− the more the new particles are

heavy, the more energy is needed to produce them

observation of their decay

Indirect search (LHCb)

virtual production of new particles− heavy particles can be produced

virtually (off mass shell) with moderate energy in the center of mass of the collision

these virtual particles affect the decay processes

− differences w.r.t. standard model prediction

Is there anything else beyond the SM at the TeV scale ?

What determines the observed pattern of masses and mixing angles of quarks and leptons ?

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The LHCb experiment @ LHC

LHCb

Atlas

CMS

Alice

LHCb : one of the 4 major experiments at LHC

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The LHCb collaboration

934 members65 institutes17 countries

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The LHCb physics program

LHCb dedicated to precision measurements of heavy flavor : comparing precision measurements and clean predictions to find evidence for new

physics flavor sector : very rich sector of the Standard Model (CKM mechanism, CP

violation, ...) with precise theoretical predictions

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The LHCb physics program

B decay to charmonium Bs mixing, CPV

B decay to open charm γ, B decay to double charm, rare hadronic B

decay

Rare decays leptonic, electroweak, radiative, LFV

Charm physics mixing and CPV, charm production and

spectroscopy

Charmless B decay B → h,h', B-> VV

Semi-leptonic B decays search for CPV in mixing, form factors, rare

decays

B hadron and quarkonia Production and spectroscopy

QCD, electroweak and exotica EW boson production, new long lived

particles

LHCb dedicated to precision measurements of heavy flavor : comparing precision measurements and clean predictions to find evidence for new

physics flavor sector : very rich sector of the Standard Model (CKM mechanism, CP

violation, ...) with precise theoretical predictions

Large measurements spectrum :

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The LHCb detector

Resolve fast BS oscillation excellent vertex resolution

Background reduction : very good impact parameter resolution

good mass resolution

good particle identification (K/π)

Collect high statistics : efficient trigger for both hadronic and

leptonic final states

Typical topology :

RICH detectorsVErtex LOcator

TRACKING system

Calorimeters

MUON system

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The LHCb detector

Resolve fast BS oscillation excellent vertex resolution

Background reduction : very good impact parameter resolution

good mass resolution

good particle identification (K/π)

Collect high statistics : efficient trigger for both hadronic and

leptonic final states

Typical topology :

RICH detectorsVErtex LOcator

TRACKING system

Calorimeters

MUON system

Installation of the Vertex Locator

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The LHCb detector

Resolve fast BS oscillation excellent vertex resolution

Background reduction : very good impact parameter resolution

good mass resolution

good particle identification (K/π)

Collect high statistics : efficient trigger for both hadronic and

leptonic final states

Typical topology :

RICH detectorsVErtex LOcator

TRACKING system

Calorimeters

MUON system

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The LHCb detector

Resolve fast BS oscillation excellent vertex resolution

Background reduction : very good impact parameter resolution

good mass resolution

good particle identification (K/π)

Collect high statistics : efficient trigger for both hadronic and

leptonic final states

Typical topology :

RICH detectorsVErtex LOcator

TRACKING system

Calorimeters

MUON system

Le trigger à muon de niveau 0 (CPPM)

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The LHCb detector specificities

Acceptance in forward region maximize the acceptance for B

decays

complementary to ATLAS & CMS

Run in low pile-up conditions lower instantaneous luminosity

than ATLAS & CMS

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Some recent LHCb results

First observation of CP violation in the decay of Bs mesons (April 2013)

Observation of an exotic particle Z(4430) [ccdu] (April 2014)

B → K*µµ : hint at new physics ? (July 2013)

Observation of Bs→μμ decays (CMS & LHCb - July 2013)

Precise search for new physics (determination of the weak phase ФS - March 2013)

And more to come ...

B → Kµµ/B → Kee : breaking lepton universality ? (σ=2.6) (July 2014)

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LHCb plans and upgrade

2010

50 fb-1 in less than 10 yearsLHCb upgrade

∫ℒ

bunch spacing

ECM 7 TeV 8 TeV

50 ns

3 fb-1 > 5 fb-1

up to 1262# of bunch crossings

ℒ (cm-2s-1)

2011 2012 2013 2014 2015 2016 2017 2018 2019 2020 2021 2022 2023 2024 2025

4∙1032

~ 2622 (nominal)

LS1 LS2 LS3 25 ns

13 TeV

> 5 fb-1 / year

> 1033

2015 : resume data taking - at higher energy- restart after 2 years !!

2018 : major upgrade of the LHCb experiment- full read-out at 40 MHz- increase instantaneous luminosity (get larger statistic)

LHCb @ CPPM

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Le groupe LHCb au CPPM

Members : 6 chercheurs

– E. Aslanides, J. Cogan, R. Le Gac, O. Leroy, G. Mancinelli, J. Serrano 1 post-doctorant

– S. Akar 4 Doctorants

– A. Morda et W. Kanso (2ème année)– M. Martin (débute en octobre)

5 Ingénieurs permanents– electronic : J-P. Cachemiche, F. Hachon, F. Réthoré– temps réel : P-Y. Duval– informatique : A. Tsaregorodtsev

Main activities Technical − level-0 muon trigger− 40 MHz read-out (LHCb upgrade)− grid middle-ware Participation to data taking (shift, piquet, ...)

Analysis− very rare decays− CP violation

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Rare decays (1/2)

Bs/d → µµ SM :

– FCNC + helicity suppress– very small branching ratio in the SM– BR(Bs → µµ) = 3.2±0.2 x 10

-9

– BR(Bd → µµ) = 1.1±0.1 x 10-10

Very sensitive to new physics contribution

Recently measured at LHCb

SM

MSSM

BR(BS → µµ)= 2.9+1.1-1.0 x10-9 Constraints on new physics models

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Rare decays (2/2)

Bs → ττ less rare than B → µµ : BR(BS →ττ) ≈ 7 x 10-7

− but can be largely enhanced by new physics very challenging experimentally τ is unstable (ex: τ → πππν !!!) No experimental limit yet

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CP Violation

ΦS in BS → J/Ψ Φ parameter sensitive to the

interference between direct decay and decay after oscillation

Bs

Bs

J/ψφ

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Probing New Physics

• Direct searches for new particles (ATLAS + CMS)

• Indirect searches (LHCb)

• Effect of virtual particles in loop processes

• New phases in loops ! new sources of CP violation

With the start of LHC operation an exciting era in the search for New Physics has begun

New Particles ?

The LHC

4 Indirect searches can be powerful, e.g observation of Bd mixing by ARGUS in 1985 pointed to heavy top No deviation yet from standard model

precision to be increased

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Conclusion

Flavor physics is a very active and exiting sector of the SMLHCb has taken the leader ship in this domain

The CPPM group is involved in key LHCb measurements

Data taking will resume shortly with a lot of new and exciting data to analyse !

You are welcome to visit us ...

Contacts: R.Le Gac: legac@cppm.in2p3.fr O.Leroy: oleroy@cppm.in2p3.fr

G.Mancinelli: giampi@cppm.in2p3.fr J.Cogan: cogan@cppm.in2p3.fr

J.Serrano: serrano@cppm.in2p3.fr

mailto:legac@cppm.in2p3.frmailto:oleroy@cppm.in2p3.frmailto:giampi@cppm.in2p3.frmailto:cogan@cppm.in2p3.frmailto:serrano@cppm.in2p3.fr

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