Upload
joella
View
18
Download
0
Embed Size (px)
DESCRIPTION
EW @ LHCb: Future Look. Ronan McNulty (UCD) EW meeting 29 th November 2011. Working Group on Electroweak precision measurements at the LHC Tuesday, Nov 29 th , 2011. Channels. Z W W/Z W+/W- (W asymmetry) A fb Low mass DY Z + jets W + charm. General Comments 2010->2011. - PowerPoint PPT Presentation
Citation preview
EW @ LHCb: Future Look
Ronan McNulty (UCD)
EW meeting 29th November 2011
Working Group on Electroweak precision measurements at the LHCTuesday, Nov 29th, 2011
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 2
Channels Z W W/Z W+/W- (W asymmetry) Afb
Low mass DY Z + jets W + charm
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 3
General Comments 2010->2011 Luminosity for 2011 is 1.1 fb-1 (factor 30) Average number of interactions is 1.7 Due to luminosity levelling, same running conditions
throughout fills and throughout year Triggers unchanged *Very stable* for analysis Since almost everything is data-driven, most
systematics are statistical in nature Factor 5.5 improvement
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 4
ZSource 2010 2011
Statistics 2.2% (2000 Z) 0.4% (60,000 Z)
Efficiency 4.0% 0.7%
Purity 0.1% 0.0%
FSR 0.0% 0.0%
Luminosity 3.5% 2.5%
2010 measurement dominated by statistics (sys. are statistical in nature)2011 dominated by luminosity. How well can we know this?
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 5
WSource 2010 2011
Statistics 0.7% (20,000 W) 0.1% (600,000 W)
Efficiency 2.8% 0.5%
Purity 3.1% 1.0% {?}
FSR 0.0% 0.0%
Luminosity 3.5% 2.5%
2010 measurement dominated by statistics (sys. are statistical in nature)2011 dominated by luminosity. How well can we know this?
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 6
How can we improve luminosity?
QED processUncertainty <1%
Well known process studied by all LHCexperiments.
• A.G.Shamov and V.I.Telnov, NIM A 494 (2002) 5156, 2002.• J. Vermaseren, Nucl. Phys. B229, 347,1983.• CMS PAS DIF-07-001• Bryan Caron, CERN-THESIS-2006-024• CERN-LHCb-CONF-2011-022
Difficulty is in selecting a pure enough signal.
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 7
Exclusive J/psi(not background subtracted)
Candidates for di-photon produced dimuons
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 8
Fit elastic and inelastic components
Shape for inelastic events
Note: this time we have simulation thatpredicts the shape for the three contributions.
Fit to signal events
Background shape from dataSignal shape from simulation.
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 9
Luminosity through pp->pmmpSource 2010 2011
Statistics 16% 2.3%
Efficiency 8% 1%
Purity 2% 0.3%
Note: Better than N improvement in 2011 due to lower average number of proton-proton interactions
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 10
W/Z (Remove luminosity)
Source 2010 2011
Statistics 2.2% 0.4%
Efficiency 2.8% 0.5%
Purity 3.1% 1.0% {?}
FSR 0.0% 0.0%
Luminosity 0.0% 0.0%
2010 measurement dominated by statistics (sys. are statistical in nature)2011 dominated by statistics & W bkg: 1% measurement looks possible
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 11
W+/W-Source 2010 2011
Statistics 1.5% 0.3%
Efficiency 0.0% 0.0%
Purity 0.2% 0.2%
FSR 0.0% 0.0%
Luminosity 0.0% 0.0%
2010 measurement dominated by statistics (sys. are statistical in nature)2011 dominated by statistics: Most sensitive experimental test of SM (<0.5%)
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 12
W asymmetryEta range 2010 2011
2 < < 2.5 0.014 0.003
2.5 < < 3. 0.014 0.003
3 < < 3.5 0.016 0.003
3.5 < < 4. 0.022 0.004
4 < < 4.5 0.058 0.010
2010 measurement dominated by statistics (sys. are statistical in nature)2011 dominated by statistics Most sensitive experimental test of SM
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 13
Indicative uncertaintieswith 2011 data
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 14
Z boson: AFB
60,000 Z with 2011 data Precision of 0.004 on Afb. Precision of ~0.001 on sin2W
(Similar to precision from Afb0l from one LEP experiment)
(see WG meeting 5th April)
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 15
*-> below Z
Backgrounds appear controllable down to 10 GeV (x~2.10-5)
Statistical uncertainty ~ as for Z Systematics under study: background description likely
to be dominant. Purity ~ 25%. Results hopefully for early 2012. Excellent method for constraining gluon pdf at low x.
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 16
Z+jets
Z sample for 2011 being analysed using anti-kt, cone 0.5.
Requires jet energy calibration difficult at LHCb EM calorimeter saturation Can’t use jet balancing techniques
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 17
W+charm
Possible once jet energy calibration understood ….
Require evidence for secondary vertices generic HF tagging IP of high pt tracks (as in Z->) D meson reconstruction
Working Group on Electroweak precision measurements at the LHC. 29.11.2011 18
Summary
W,Z limited by luminosity uncertainty which can improve using pp
Ratios become systematic limited at ~ 1% New measurements: Afb, low mass DY,
Z+jets, W+charm