a fb at lhc
DESCRIPTION
A FB at LHC. Myfanwy Liles (University of Liverpool) Ronan McNulty (University College Dublin) Tara Shears (University of Liverpool). LHCEWWG 5.04.2011. Outline. Is it worth trying to measure A FB at LHC? Rather simple and unsophisticated study Horace Pythia - PowerPoint PPT PresentationTRANSCRIPT
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Ronan McNulty, LHCEWWG, 5.04.2011 1
AFB at LHC
Myfanwy Liles (University of Liverpool)Ronan McNulty (University College Dublin)Tara Shears (University of Liverpool)
LHCEWWG 5.04.2011
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Ronan McNulty, LHCEWWG, 5.04.2011 2
Outline
Is it worth trying to measure AFB at LHC?
Rather simple and unsophisticated study Horace Pythia
Motivate discussion and ideas
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Ronan McNulty, LHCEWWG, 5.04.2011 3
Current precision on sin2W
Unsatisfactory that two most precise measurements are >3 apart, and that W.A. is marginally consistent with either.
Would like to make measurement with precisionof ~0.0001.
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Ronan McNulty, LHCEWWG, 5.04.2011 4
AFB away from Z pole Strong dependence with mass due to -Z
interference. (To first order, zero on pole).
HORACE: O()+-ind. 7TeV.All rapidities.
“Asymmetry greater further from pole”
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Ronan McNulty, LHCEWWG, 5.04.2011 5
AFB away from Z pole On pole, due to different RH, LH Z coupling… Small positive value
HORACE: O()+-ind. 7TeV.All rapidities.
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Ronan McNulty, LHCEWWG, 5.04.2011 6
AFB in muon channel at LHC is about 5 times larger than at LEP.
But sensitivity coming more from Al rather than Au or Ad
AFB on Z pole
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Ronan McNulty, LHCEWWG, 5.04.2011 7
Where are we most sensitive?
Greatest sensitivity per event at 82 GeV
About 2/3 that sensitivity at 91 GeV
But much more stats.
So measurement on pole appearsmost sensitive to sin2
far from pole
near pole
HORACE: Born7TeV.All rapidities.
HORACE: Born7TeV.All rapidities.
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Ronan McNulty, LHCEWWG, 5.04.2011 8
Problems for LHC
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Ronan McNulty, LHCEWWG, 5.04.2011 9
Going forward increases AFB
HORACE: Born7TeV.89.2<m<93.2.
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Ronan McNulty, LHCEWWG, 5.04.2011 10
Going forward increases sensitivity…
HORACE: Born7TeV.86.2<m<96.2.
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Ronan McNulty, LHCEWWG, 5.04.2011 11
HORACE: Born7TeV.
Stat uncertainty 10fb-1
Stat uncertainty 50fb-1
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Ronan McNulty, LHCEWWG, 5.04.2011 12
50fb-1 at 14 TeV measures sin2~0.0001
HORACE: Born14TeV.
Stat uncertainty 10fb-1
Stat uncertainty 50fb-1
1fb-1
10fb-1
50fb-1
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Ronan McNulty, LHCEWWG, 5.04.2011 13
50fb-1 at 14 TeV measures sin2~0.0001
HORACE: Born14TeV.
Stat uncertainty 10fb-1
Stat uncertainty 50fb-1
1fb-1
10fb-1
50fb-1
How confident are we:- of theory? - of PDF uncertainties? -of detector systematics?
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Ronan McNulty, LHCEWWG, 5.04.2011 14
Uncertainty due to PDF
MSTW Eigenvector number
AFB c
alc
ula
ted
For 3<yZ<4
0.0004
Uncertainty from PDF(from one PDF set)about the same asstatistical uncertainty.
With time, this shouldimprove (~ 50%?)
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Ronan McNulty, LHCEWWG, 5.04.2011 15
Uncertainty due to PDF
0.0004
Difference betweentwo (old) PDF setsabout the same asstatistical uncertainty.
HORACE: Born7TeV.86.2<m<96.2.
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Ronan McNulty, LHCEWWG, 5.04.2011 16
Conclusions
Is it worth trying to measure AFB at LHC?
…. Probably.