high precision and new cp violation measurements with lhcb michael koratzinos, cern eps hep 99...
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![Page 1: High precision and new CP violation measurements with LHCb Michael Koratzinos, CERN EPS HEP 99 Tampere,15 July 1999](https://reader036.vdocuments.us/reader036/viewer/2022062518/5697bf911a28abf838c8e52e/html5/thumbnails/1.jpg)
High precision and new CP violation measurements
with LHCb
Michael Koratzinos, CERN
EPS HEP 99Tampere ,15 July 1999
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Brazil
France
Germany
Italy NetherlandsPRC Romania Spain
Switzerland
Ukraine
UK
USA
The LHCb Experiment
Poland Russia
Finland
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The LHCb collaboration: brief history & future
• Aug 1995: Letter of Intent (~30 institutes, 171 collaborators)
• Feb 1998: Technical Proposal (42 institutes, 336 collaborators)
• July 1998: Experiment approved
• 2000-2002: Technical Design Reports
• 2005: Ready to take data from day one of LHC operation
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Overview
LHCb is an experiment that will probe the Standard Model in the LHC era by performing accurate CP violation measurements in the B sector.
The strength of the experiment is that it provides a complete package: it will not only measure accurately some CP violation parameters, it will measure enough parameters and in enough different ways to overconstrain the Standard Model.
However, here I will give a selected overview on a small number of channels, concentrating on channels that are either difficult for earlier generation experiments or can be done with much greater precision in LHC.
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Strengths of the LHCb experiment•Statistics
•LHC is a copious B factory (b500 b, 1012 bb per year)
•Trigger designed to be highly efficient for B physics
•Particle ID - essential for background suppression in some channels
•Two RICH counters ensure good K- separation in the required momentum range (1 to 150 GeV)
•Accurate vertexing - essential for good proper time resolution
•Silicon vertex detector in a Roman Pot (first tracking measurement close to vertex)
•Good mass resolution - in Bs DSK: m = 11 MeV/c2
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The LHCb Detector
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Angles of CKM Unitarity Triangles(and decay modes to measure them discussed in this talk)
Vtd Vtb+Vcd Vcb
+Vud Vub= 0 Vtd Vud
+Vts Vus+Vtb Vub
= 0
Vub
Vcb
Vtd
Vub
Vtd
Vts
Bd J/KSBd D
Bd
Bs J/
Bs DSK
(,)
(0,0) (1,0)
BsKKBd
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Here we will have results from earlier generation experiments but LHC will provide high statistics
•B0 J/Ks (measures sin(2)); sin20.05 by 2005
•High statistics at LHC (LHCb: 45k tagged events per year) can reduce this ultimately to 0.006 Can probe direct CP violation
•B0 (measures (2 +2) or (-))
•B factories total: <1000 events by 2005; LHCb: 7k events/year (assuming Br=0.7X10-5)
•Particle ID essential
•BUT Penguin diagram uncertainty: theory brick wall at 2-5 degrees if P/T 10% - Challenge to theory!
•B0 : Alternative channel for that bypasses the penguin problem; multi parameter fit, so need statistics (>5k events) [LHCb: 1k events/year]
•B0d D*+ ,a1
+ measures () - need large statistics; LHCb can get >500k events/y (D*+ and D*a1
+) ; 100 in 1 year. Theoretically clean.
Bd sector
Need to know P/Tto better than 10%
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Bs sector•No results from B factories
•Measurements require sensitivity to Bs oscillations - good proper time resolution is needed
•Bs J/ measures sin(2) no particle ID needed, also good for ATLAS/CMS
•Bs DsK measures (2 ); Ds background , so use RICH
•Bs KK use theory to relate to Bd allows and 2 to be determined simultaneously
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• equivalent of Bd J/ KS
• CP asymmetry allows to extract the phase of Bs mixing amplitude, i.e. angle
Bs J/
iVVJB
iVVKJB
tstbs
tdtbSd
2exp:/
2exp:/2*
2*
• decay into spin-1 particles:J/ can be CP-odd or CP-even(depending on angular orbital momentum)
need angular analysis to separate contributions
• Good proper time resolution needed
• can be done by ATLAS/CMS/LHCb with similar sensitivity
LHC-wide precision measurement
Good place to look
for new physics
Current limit
[B physics working group]
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Extraction of from 4 time-dependent decay rates, then use from J/ to get
Theoretically clean
• hadron trigger
• proper time resolution
• mass resolution
• K/ separation (RICH)
• hadron trigger
• proper time resolution
• mass resolution
• K/ separation (RICH)kill Bs Ds background
Essential features:Bs DsK+, Ds
+K
~ 2.5 k events / year with S/B > 10 (reconstructed & tagged)
depends on , ms,and strong phase(will be extracted as well)
No penguindiagram
contributions
~ 10o in one year
Can only be done at LHCb
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Bs KK
Used in conjunction with B to extract and
Can only be done at LHCb•Need Hadron trigger•Need Particle ID•Need good proper time resolution
LHCb: 4k reconstructed and tagged events/y
Under certain assumptions,20 for =760 in 5 years
ms=20ps-1
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Conclusions•LHCb will perform precision physics in the LHC era•Its key features of
•Efficient trigger•Excellent Particle identification •Good mass and decay time resolutions
will help to perform a multitude of measurements to probe the Standard Model•The Bd sector will benefit from high statistics
•B0 J/Ks can probe direct CP violation •B0 large theoretical uncertainties due to penguin diagrams •B0 multi parameter fit avoids the penguin problem•B0
d D*+ ,a1+ theoretically clean measurement for
•The Bs sector will be exploited to good effect•Bs J/LHC-wide precision measurement•Bs DsK theoretically clean measurement, LHCb specific•Bs K K LHCb specific measurement