high precision cp violation physics at lhcb
DESCRIPTION
Meeting of the EPFL Research Commission, EPFL, November 30, 2004. High precision CP violation physics at LHCb. presented by Olivier Schneider. On-going, long-term project supported in Lausanne since several years by SNSF and FORCE grants (FORCE = Fonds pour la Recherche au CERN): - PowerPoint PPT PresentationTRANSCRIPT
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)
Num
ber
of o
bser
ved
deca
ys in
, N
(K
)
K0
K0
QuickTime™ and aTIFF (Uncompressed) decompressorare needed to see this picture.CP is violated !
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 3
Matter is made of fermions (spin 1/2) Each fermion has an anti-matter counterpart
Standard Model (SM) of particle physics
d
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s
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d sd
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u
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d u
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K0
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K 0
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−
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+
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s bd
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b
€
B0
€
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
€
proton
Quarks can only appear as “colourless” combinations (=hadrons):
€
s
€
K0 {
€
d
€
d€
u
€
u
€
d
€
W +
€
} π +
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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)
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 4
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
€
d' s' b'
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟=
Vud Vus Vub
Vcd Vcs Vcb
Vtd Vts Vtb
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
d
s
b
⎛
⎝ ⎜ ⎜
⎞
⎠ ⎟ ⎟
€
b
€
u
€
W−
Quarks
€
Vub
€
d ' s ' b '
⎛
⎝
⎜ ⎜
⎞
⎠
⎟ ⎟=
Vud* Vus
* Vub*
Vcd* Vcs
* Vcb*
Vtd* Vts
* Vtb*
⎛
⎝
⎜ ⎜
⎞
⎠
⎟ ⎟
d s b
⎛
⎝
⎜ ⎜
⎞
⎠
⎟ ⎟
€
b
€
u
€
W +
Anti-quarks
€
Vub*
mass states
weak states CKM matrix
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 5
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
€
VCKMVCKM† =
1 0 00 1 00 0 1
⎛
⎝ ⎜
⎞
⎠ ⎟
€
⇒ VudVub* + VcdVcb
* + VtdVtb* = 0
“Unitarity triangle” (area CP violation)
responsible for CP violation
Im
Re€
VtdVtb*
VcdVcb*
€
VudVub*
VcdVcb*
0 1
€
1
€
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€
W
€
W
€
b
€
B0 ⎧ ⎨ ⎪
⎩ ⎪
€
d
€
b€
d
€
⎫ ⎬ ⎪
⎭ ⎪ B 0
€
t
€
t
B0–B0 oscillations: “Box” diagram–€
b
€
Bs0
⎧ ⎨ ⎪
⎩ ⎪
€
s
€
t
€
W +
€
s
€
s
€
} φ
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s
€
s
€
} φ
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
?
? ? ??
?
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 7
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
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 8
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
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 9
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
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 10
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
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 11
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)
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 12
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
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 13
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
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 14
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
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 15
LPHE’s construction commitments
VELO
Off-detector electronics "TELL1"
Vertex locator analogue links Inner Tracker (Si detectors)
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 16
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
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 17
TELL1 readout board
Credit-card PC Experiment
control system
clock
QuickTime™ and aTIFF (LZW) decompressor
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
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 18
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
€
W
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W
€
b
€
Bs0
⎧ ⎨ ⎪
⎩ ⎪
€
s
€
b€
s
€
⎫ ⎬ ⎪
⎭ ⎪ B s
0
€
t
€
tVts
Vts
Fast Bs oscillation, proper-time resolution crucial
00– Bs–Bs oscillation frequency: ms |Vts|2
0
O. Schneider, Nov 30, 2004 Meeting of EPFL Research Commission 19
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.
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.
CP
QuickTime™ and aTIFF (Uncompressed) decompressor
are needed to see this picture.