ongoing physics analyses and future projects
DESCRIPTION
Ongoing physics analyses and future projects. Véronique Boisvert Marshak Fellow For the CDF Rochester group. Rochester DOE Site visit July 18 th 2006. Focus of the group. Phys. Rev. Lett. 96, 211801 (2006) J. Lee , G. De Lentdecker Already referred to in 3 papers. - PowerPoint PPT PresentationTRANSCRIPT
1
Ongoing physics analyses and future projects
Véronique Boisvert
Marshak Fellow
For the CDF Rochester group
Rochester DOE Site visit July 18th 2006
2
Focus of the group Electroweak interactions as probe of new Physics
W and Z bosons: W charge asymmetry Z d/dy distribution Z Forward Backward Asymmetry (AFB) Search for Z’e+e-
Top quark: Top Mass Charged Higgs production Flavor Changing Neutral Currents Top Charge
Search for new quark states: Exotic bottom baryon search
Phys. Rev. Lett. 96, 211801 (2006)J. Lee, G. De Lentdecker
Already referred to in 3 papers
Public result for the matrix element method in Lepton+Jets golden channel
using 318pb-1
E. Halkiadakis (now Rutgers University professor)
Phys. Rev. Lett. 96, 042003 (2006) R. Eusebi (now FNAL Lederman
fellow), A. Hocker (now FNAL scientist) Already referred to in 2 papers
New analysis started: G. Yu, Y.S. Chung
Legend:Past yearCurrent and future workPlan for public result
Analysis completed and received best Rochester undergraduate thesis award
G. Yu, S. Field , Y. S. Chung
3
W Charge Asymmetry u quark carries higher fraction of proton momentum!A(yW ) =
d + / dyW −d− / dyW
d + / dyW +d− / dyW≈
u(x1)d(x2 )−d(x1)u(x2 )u(x1)d(x2 ) +d(x1)u(x2 )
anti-proton direction proton direction
Get constraints on the PDF’s of the proton Important QCD information Helps to better model production rapidity
of heavy systems (W, Z, tt, etc.) Reduces systematic uncertainty from
acceptance corrections
B.Y. Han, A. Bodek, Y. S. Chung, E. Halkiadakis, K. McFarland
x1,2 =MW
se±yW
**
V-A impactsW production kinematicsW decay kinematics
P =(1±cos * )2
4
W Charge Asymmetry Analysis method: Number of W vs yW
Use MET for P: missing Pz! Use MW constraint to get 2 possible yW
Weight each of them depending on: Angular distribution
W cross section
Depends on A! Iterate!
Araw Atrue: Corrections:
wt1,2± =
P±(cos1,2* ,y1,2 , pT
W )±(y1,2 )P±(cos1
* ,y1, pTW )±(y1) + P±(cos2
* ,y2 , pTW )±(y2 )
P±(cos * ,yW , pTW ) =A{(1mcos * )2 +Q(yW , pT
W )(1±cos * )2}
MET
Acceptance and smearing
QCD Background subtraction from dataUse new technique of fitting e isolation shape
Charge misidentification using Z e+e- data
q(p)+q(p)
q(p)+q(p)
q(p)+q(p)
q(p)+q(p)
5
W Charge Asymmetry
Systematics: E scale (ET(e), MET) PDF uncertainty:
Angular Distribution W cross section
Background Material effect,
Acceptance 1fb-1 prediction Investigating East-West
Asymmetry discrepancy Expect public result with
343pb-1 by end of summer
6
d/dy distribution of the Z boson Probe high momentum fraction of the
proton at high rapidity: Use Plug-Plug region to reach |y|<2.8! Analysis uses 850pb-1
J.Y Han, A. Bodek, H. Budd, W. Sakumoto, Y. S. Chung
d(γ* / Z)dy =
Nsig(y)−Nbkg(y)AZ(y)εZ(y)εtrig(y)εzvtx(y)L
central electron ID efficiency ~83%, ~96%plug electron ID efficiency ~83%Z vertex luminosity acceptance ~96%
ID triggerZ efficiency in central-central ~90% ~100%Z efficiency in central-plug ~70% ~95%Z efficiency in plug-plug ~71% ~98%
7
d/dy distribution of the Z boson QCD background predictions:
Isolation fitting method Use data to get signal and
background isolation shape (subtract W+jets from background selection using MC for shape and data for normalization)
Systematics: Background estimation Material
Remaining: 1fb-1
Electroweak backgrounds dependence of ID efficiencies
Already started public result procedure
Zcc0.420.09%
(Zee) : 251.15± 1.04(stat.)0.31(sys.) pb
8
Measurement of Z AFB
Dilepton decay of γ*/Z has forward backward angular asymmetry AFB=(NF-NB)/(NF+NB) Probe V-A nature of weak
interaction New technique:Response
Matrix inversion Rij=P(observed in bin i | true
value in bin j) Observed =R * True True = R-1 * Observed True = R-1 * (Observed - bckg)
J. Lee, G. De Lentdecker, K. McFarland
9
Measurement of Z AFB Backgrounds:
QCD backgrounds New technique: fitting isolation
shape using templates: Electron: data at Z pole Jets: high pt electron data, remove
W/Z events Electroweak backgrounds: use MC
Systematics: E scale and resolution, Response
matrix, Background, material, PDF 364pb-1 result already public Updating with 1fb-1
Extract coupling constant, sin2w
10
Measurement of Z AFB
Other method: increase sensitivity by fitting cos* in mass bins
Worry about acceptance, smearing, QED radiation and fit convergence
Backgrounds: Use tools from matrix inversion
method Systematics:
Use results from matrix inversion method + worry about NLO QCD distorsion of cos* distribution
Public result with 1fb-1 around end of summer
J. Lee, G. De Lentdecker, K. McFarland
d̂ ( ff → e+e−)dcos * ∝ CF 1+ cos *( )
2+CB 1−cos *( )
2⎡⎣
⎤⎦• Acc(cos * )
Fit function minimizing CF and CB
AFB =3 CF −CB( )4 CF +CB( )
11
FCNC in the Top sector FCNC in the SM only
allowed by penguins BR<10-12
New Physics strongly enhances BR (~10-3-10-4)
MSSM, 2HDM, dynamical EWSB, warped ED, etc.
Looking at tt Wb Zc Standard: W jj, Z ll
(dilepton from Z + 4 jets) Also: W l, Z ll (trilepton
+ 2 jets + MET)
J. Gimmell, U. Husemann, (K. McFarland), P. Tipton, Harvard, UCLA
12
FCNC in the Top sector Backgrounds:
Z+jets: use sophisticated Alpgen MC and validate with data distributions
Z + 4 jets Zbb + ≥ 2 jets Zcc + ≥ 2 jets
SM Top Diboson (WZ) Jets faking leptons
For greater sensitivity separate events according to ≥ 1 b tag = 0 b tag Optimize event selection based on
best expected limit (Feldman-Cousins including systematics)
Heavy Flavor fraction not well modeled, new: use templates and fit the data to get fraction
13
Top Charge X W+b or W+b (and cc)?
If exotic q=-4/3, better EW fit hep-ph/9810531, hep-ph/9909537
Ingredients: 1) Charge of W
Charge of lepton 2) Pairing between W and b
Dilepton: M2lb value
L+J: 2 algorithm 3) Flavor of b jet: JetQ
algorithm Measure dilution in dijet
data
V. Boisvert, W. Hopkins (undergrad), M. Schwarz (undergrad),K. McFarland, MSU
?
b or b ?b or b ?
?
Reco bReco b
True b
True b
14
Top Charge Dilution in dijet data:
Look at correlation between and away jet
Corrections: Non-b fraction on side
and away jet side Template fitting using
data b c fraction (MC) B mixing fraction (MC)
Extrapolate from dijet to tt Backgrounds:
Investigated if backgrounds mimic more SM top or exotic quark
Mostly symmetric between SM top and exotic
Jet axis
b tagged
Soft PTrel
Away Jet
b tagged
x
x
Confidence Limit extraction Using Profile Likelihood method
and studied sensitivity of: dilution uncertainty: very
sensitive amount of backgrounds: not very
sensitive etc.
Working hard to get preliminary public result with 1fb-1 by end of summer…
15
Charged Higgs Search from Top decays
In SUSY get 5 Higgs bosons, including H
Direct production is small at Tevatron
Look for ttWb Hb Low tan, H cs
Use Top mass 2 fitter M(Wl)=80.4GeV/c2,
unconstrained M(Wjj) Deciding on b tagging
requirements M(H) resolution improvement
using 5th leading jet Sensitivity studies underway
G. Yu, Y.S. Chung, A. Bodek, U. of Chicago
16
Conclusion Rochester members involved in crucial CDF
analyses that will potentially lead to NP discovery! remain relevant even after the LHC turn on!
Isolation fitting method for the QCD background Precise W rapidity method b flavor tagging in high pt environment
Students and post-docs primary authors of complex and challenging projects New analyses and/or novel techniques!
Rochester scientists and faculty provide the necessary infrastructure to the realization of these analyses and the education of the young members!
17
Backups
18
W charge asymmetry
measuringasymmetry
the closest asymmetry to data
assumedsample
F1 min( )2
new assumedsample
Fn
reconstructionInputdata
YesNo
if no,
(yW) vs. PDF
19
Rediscover the Top quark Use Top physics to establish
techniques: Cross section b tagging Background treatment
What about top charge? Measure em couplings using ttγ
(hep-ph/0106341)
R=(γ in t prod)/(γ in t decay) Irreducible bckg from radiation
off q,q’ (not an issue at LHC…) Tevatron: need 20fb-1 to rule out
-4/3 at 95%CL LHC: need 10fb-1 to measure
charge to 10%
γ
γ
γ
γ