High precision CP violation physics at LHCb

High precision CP violation physics at LHCb

Meeting of the EPFL Research Commission,EPFL, November 30, 2004

• On-going, long-term project supported in Lausanne since several years by SNSF and FORCE grants(FORCE = Fonds pour la Recherche au CERN):

Co-applicants:Prof. A. Bay, LPHEProf. T. Nakada, LPHEProf. O. Schneider, LPHEDr. Minh-Tam Tran, LPHE

• Main project of the LPHE (Laboratoire de Physique des Hautes Energies)

• LHCb experiment in preparation at CERN by a large international collaboration

presented by Olivier Schneider

Contents:

– CP violation, B physics …

– LHCb physics goals

– LHCb experiment

– LPHE’s involvement and responsibilities

O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 2

CP symmetry: textbook example

K0

CP mirror

K0

Parity P: left rightCharge conjugation C: q –q

CP: matter antimatter

If CP is conserved, the probability for a K0 to decay to after a certain proper time t should be the same as

that of an anti-K0.

CPLEAR experiment at CERN, Phys. Lett. B 363, 243 (1995)

Measured proper time t / (KS)

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ber

of o

bser

ved

deca

ys in

, N

(K

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K0

K0

QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.CP is violated !


Matter is made of fermions (spin 1/2) Each fermion has an anti-matter counterpart

Standard Model (SM) of particle physics

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d u

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K0

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K 0

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B0

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Bs0

Electric charge [e]

Colour charge

Leptonselectron e muon tau –1

noneutrino e neutrino neutrino 0

Quarksup u charm c top t +2/3

yesdown d strange s bottom b –1/3

1015 muud

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proton

Quarks can only appear as “colourless” combinations (=hadrons):

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} π−Feynman diagram:

time

Forces are described as exchange of bosons (e.g. photon for the electromagnetic, W± and Z for the weak interaction)


Higgs field (yet to be discovered !) generates mass of particles Quark mass eigenstates are different from weak eigenstates

quark mixing matrix (Cabibbo, Kobayashi, Maskawa)

CP violation in the Standard Model

Different mixing matrix for quarks and anti-quarks CP violation

Vij proportional to transition amplitude from quark j to quark i

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d' s' b'

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Vud Vus Vub

Vcd Vcs Vcb

Vtd Vts Vtb

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mass states

weak states CKM matrix


CKM matrix:—complex and unitary 4 parameters (e.g. 3 angles and 1 phase)

—6 unitarity triangles

—most sensitive experimentaltests on the two unsquashedtriangles, with transitionsinvolving b quarks

CP violation in the Standard Model

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“Unitarity triangle” (area CP violation)

responsible for CP violation

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B0, B 0 decays and Bs

0, B s0 decays

most suitable to study CP violation

O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 6€

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B0–B0 oscillations: “Box” diagram–€

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Bs decay: “Penguin” diagram0

Cosmological argument:—Our Universe displays obvious matter-antimatter asymmetry—Evolution from symmetric situation at Big Bang requires CP (Sakharov)—CP violation in SM far too small to explain other sources of CP must exist

New particles ? —Motivated from theories of grand unification, supersymmetry, dark matter, …—Almost every SM extension implies new sources of CP—May be observed directly (if produced in high-energy collisions),

or indirectly in “loop” processes (even at lower energies) Examples of loop processes:

Physics beyond the Standard Model ?

Standard Model New Physics

?

? ? ??

?


Physics goals of LHCbCKM unitarity triangle as measured today

High-precision measurements of CP violation with B decays

and study of rare B decays search for New Physics

Possible impact of an LHCb measurement

Possible scenario in 2007 before LHCb


LHCb(B physics, CP violation)

LHC tunnel (27 km = 0.09 ms)

Genève

CERN

LHC = Large Hadron Collider

ATLAS(Higgs, ...)

CMS (Higgs, ...)

ALICE(heavy ion collisons,

quark-gluon plasma)

Start operation in 2007

Proton bunch spacing: 7.5 m = 25 nsProton-proton collisions at 14 TeV

World’s largest beam energy and most intense source of b hadrons

Rates at LHCb:

~16 MHz of pp interactions 0.1 MHz of b hadrons

Huge statistics


LHCb detector

VELO

VELO: Vertex Locator (around interaction point) TT, T1-3: Tracking stations RICH1-2: Ring Imaging Cherenkov detectorsECAL, HCAL: CalorimetersM1-5: Muon stations

proton beam

proton beam collision

point

1 mm

B

B = 1.5 ps


Technical challenges Imposed by LHC environment and physics requirements Examples: Typical/nominal values

— Fast detectors and front-end electronics 25 ns cycle— Radiation-hard detectors and front-end electronics ~1014 neq/cm2/y at r = 8 mm— Pattern recognition in dense environment ~72 rec. tracks per bb event— Ability to perform precise measurements

• Lowest possible amount of material (tracking region) 30% X0

• Impact parameter and vertex resolution z = 45 m on interaction point• B proper time resolution 40 fs• B mass resolution 15 MeV/c2

• Particle identification (e.g. K/ separation)— Very selective and efficient multi-level trigger

for interesting B decays (L0 hardware & L1, HLT software) 16 MHz 1 kHz (so 1/16’000)

— Huge dataset handling, large scale computing(distributed analysis, GRID, …) 21010 evts/year * 100 kB/evt

= 2 PBytes per year


LHCb now in construction phase

R&DPrototypes

Construction

Data taking

Analyses

Publications (physics results)

We are here

1995

2010

2015

?

1990

1998

1993

200020022004

2007

Technical Proposal& CERN approval

Technical Design Reports

LHC startup

LHCb collab. formedLetter of Intent

Pre-cursor ideasExpressions of interest

1st physics paper

LHCb dipole magnet installed in cavern viewed along beam line towards interaction point

Fe yoke (1.45 kt) Al coil (2 25 t) 4.2 MW power at 1 T field

~ 4 m

Detector construction underway:– Installation until end 2006– Commissioning in 2007 until LHC beam (summer)


LHCb collaboration ~500 scientists, 45 institutions, 13 countries

— Memoranda of Understanding:• construction, M&O, computing

— Constitution (defining organisation) Organization

— Collaboration board (one member/institution)— Management:

• spokesperson, technical coordinator, resources coordinator

— Project leaders:• different sub-detectors, trigger, physics,

reconstruction, software, computing, …— Coordinators:

• electronics, test beam, coordination panels

Monitoring, imposed and controlled by CERN— LHC committee (scientific and technical review)— Resources Review Board

Prof. Tatsuya Nakada (EPFL), spokesperson since 1995, recently re-elected for a new term until Feb. 2008

Prof. Olivier Schneider (EPFL),physics project leader since 2000

Gérald Parisod, RRB member

Two Swiss institutes:EPFL and UniZH

Prof. Ueli Strauman (UniZH),Si tracker project leader


Technical Design Reports

2003

1999CERN

2000CERN, France,

Romania, Russia,Spain, Ukraine

2001CERN, Germany,

Netherlands, Switzerland, UK, Ukraine

2001Brazil, CERN,Italy, Russia

2000CERN, Italy, UK

2001CERN, China, France

Switzerland, UK

2002Germany, Spain

Switzerland

2003Brazil, CERN,

France, Italy, Poland,Switzerland, UK

2001China, Germany

Netherlands, Poland

11th TDR on on computing

due in 2005


LPHE’s responsibilities in LHCb VELO and readout electronics: Prof. A. Bay

— Development of an off-detector electronics board for the VELO became a global project within LHCb for (almost) all detectors: TELL1, coordinated by A. Bay (final R&D and production)

— Transmission lines and power supplies for the VELO Inner Tracker: Dr. Minh-Tam Tran

— R&D and construction of tracking stations downstream of the magnet, close to the beam pipe (Si detectors):ladder assembly & bonding, mechanics, cooling, …

TELL1 and Inner Tracker maintenance and operations (during commissioning and several years of data-taking)

Trigger and physics: SNSF Prof. T. Schietinger & Prof. O. Schneider— Monte Carlo performance studies and overall detector optimization— Development of software trigger algorithms (L1, HLT)

and physics reconstruction algorithms

Need to rely on our electronicsand mechanics workshops

VELO line adaptor

Inner Trackergluing jig


LPHE’s construction commitments

VELO

Off-detector electronics "TELL1"

Vertex locator analogue links Inner Tracker (Si detectors)


Inner tracker Design:

— 3 stations (T1, T2, T3)— 4 boxes per station— 4 Si planes (xuvx) per box— 504 Si sensors— Si strip pitch 198 m— 129’024 detection channels—1008 Beetle readout chips with

analog pipeline (L0 buffer, 4 s)— Big issue: minimize material

Construction:—EDR in Dec 2004—Start construction early 2005

(assembly in Lausanne and CERN)—Installation finished end 2006

Be

beam pipe

320 m Si

~130 cm 45 cm

410 m Si

C6F14 coolant(–15C)

readout connectors

5C

~ 6 m 4.5 m


TELL1 readout board

Credit-card PC Experiment

control system

clock

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are needed to see this picture.

Fully developed at LPHE

Final design ready

~300 boards to be built for LHCb HLT “yes”

storage

to HLT

Optical or analog interfaces

Optical or analog interfaces

Font-end (on-detector)

electronics

L0 “yes”

L0 “yes”

1 MHz

Pre-processor FPGA L1 buffer (58 ms, 58 kevts)

Sync & link FPGA

Gigabit ethernet interface

CPUfarm

(~1800)

to L1

L1 “yes” 40 kHz


Physics performance study (example)

—Very interesting measurement to be done with 1st year of data

—Needed for the observation of CP asymmetries with Bs decays

Expected unmixed Bs Ds sample

in one year of data taking (fast MC)

Full MC

After 1 year, can observe5 signal if ms < 68 ps1

well beyond SM prediction

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tVts

Vts

Fast Bs oscillation, proper-time resolution crucial

00– Bs–Bs oscillation frequency: ms |Vts|2

0


Summary

CP:—fundamental (a)symmetry of nature (matter vs antimatter)—cosmology calls for CP violation beyond Standard Model

LHCb:—will exploit LHC’s huge b-hadron production to measure

precisely CP violation and search for New Physics—detector R&D finished, construction started—data-taking as soon as LHC turns on (2007)

LPHE @ EPFL:— plays a leading role in LHCb collaboration—responsible for crucial parts of the detector

40 years after its discovery in 1964, CP violation may still reveal secrets about its origin. We hope it will be the case in LHCb.

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CP

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High precision CP violation physics at LHCb

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