physics results with w/z from tevatron marco rescigno infn/roma on behalf of cdf and d0 collab....

Physics results with W/Z from Tevatron

Marco RescignoINFN/Roma

On behalf of CDF and D0 collab.Moriond EWK, 6-13 2010

Topics• W mass and width• W asymmetry and Z/*

differential x-section• Z/W + jet • Z/W + Heavy Flavor

jets

M.Rescigno - Moriond EWK 2010 2

Introduction & Outline

• Precision Physics Mw

W

Impact on EWK global fits• W/Z prod. properties as a probe for

PDF W charge asymmetry Z boson rapidity• QCD test in high Q2 multi-parton final states W + jets Z + jets


MW

• High precision measurement from Tevatron (0.05%) requires precision lepton momentum and recoil momentum calibration (driven by the Zll statistics)

• World best result from D0 [Phys. Rev. Lett. 103, 141801 (2009 )] See YSF1 S.Yacoob this afternoon

• Tevatron average more precise than LEP direct measurement!

0.2 fb

-

1

1.0 fb

-

1


MW

• MW vs Mtop + EWK precision observables favor low mass SM Higgs

• Mtop+ EWK fits predict MW mass to 20 MeV/c2

• MW measured to ~10 MeV/c2 highly desirable, could hint to New Physics

• CDF (2 fb-1) expects ~ 15 MeV/c2 stat uncertainty per channel

• Controlling syst. at that level requires control of higher order QED radiation and PDF theory connection


*W = 2.033 ± 0.072 GeV/c2

PR

L. 1

03, 2

31802 (2

009)

W = 2.034 ± 0.072 GeV/c2

PR

L 1

00,

071801(2

008)

W results

• Fit to the high-end tail of the transverse mass peak

• CDF/D0 both surpassed in Run II average LEP2 direct measurements

• SM prediction by far more precise* Tevatron average do not

include yet new D0 result. The soon to be released one will improve by 10 MeV

http://scitation.aip.org/getpdf/servlet/GetPDFServlet?filetype=pdf&id=PRLTAO000100000007071801000001&idtype=cvips&prog=normal


Rare W Decay

• Clean final state : enhanced by anomalous -W couplings.

• SM branching fraction : 10-6 - 10-8

• Becomes sensitive to new physics with data samples of several million W

W-

W-

206 candidate events in signal (75 < Mπγ < 85 GeV) region

NEW


W asymmetry• Phys. Rev. Lett. 101,

211801 (2008) 0.70 fb-1 (electron)

• D0 note E31 4.9 fb-1 (muons)• Phys. Rev. Lett. 102,

181801 (2009) 1.0 fb-1 (electron)

• In p-pbar collisions W+ tend to go in p direction: u quark carries more momentum than d on average

• For lepton asymmetry consider also V-A decay: e+ in pbar direction (for W+ production off valence quarks)

• W± charge asymmetry sensitive probe of the fractional momentum difference b/w u and d quarks

NEW


W asymmetry

• Compared to CTEQ 6.1/6.6 and MRST PDF sets. Good agreement and total experimental uncertainty significantly smaller than PDF uncertainty band


W asymmetry• Compare D0 and CDF

measurements in 2 lepton pT bins and with CTEQ 6.6

• Experiments ~agree • Effort ongoing to

understand discrepancy with current PDF at high pT


CDF 2.1 fb-1 (electron) arXiv:0908.3914

σ = 256.6 ± 0.7(stat.) ± 2.0 (syst.) pb

d/dy(Z/e+e-)

• Probe low-x PDF through high rapidity Drell-Yan pairs

• Compare with CTEQ and MRST/MSTW2008

• Good agreement within quoted uncertainty

CDF Run II preliminary


Vector Bosons + jets

• W/Z used as a clean probe of high Q^2 processes with multi-parton final states

• High statistic available at the Tevatron allow detailed comparisons with: NLO calculations available up to 3 jets for certain processes Matched Tree Level Matrix-Element + parton shower MC (Alpgen,

Sherpa)• Valuable tools for “discovery” physics that need to be validated• Crucial backgrounds for top physics and Tevatron Higgs

searches

• CDF W(e)+jet Phys. Rev. D77, 011108 (2008).

• CDF Z(ee)+jet Phys. Rev. Lett. 100, 102001 (2008)

• CDF Z()+jet CDF QCD web page• CDF Z(e+)+ b-jet Phys. Rev. D79, 052008

(2009) • CDF W(e+)+b-jet arXiv: 0909.1505. Sub.

to Phys. Rev. Lett • D0 Z()+jet Phys. Lett. B 682, 370 (2010)• D0 Z(ee)+jet Phys. Lett. B 678, 45 (2009)

M.Rescigno - Moriond EWK 2010 12Page 12

WW + Inclusive Jets + Inclusive Jets• CDF CDF WW+jets analysis: +jets analysis:

320/pb320/pb• W(W(ee)) selection: selection:

ee: E: ET T > 20 GeV, |> 20 GeV, || < 1.1| < 1.1

: missing energy : missing energy > 30 GeV> 30 GeV

MMT T ((WW) > 20 GeV/c) > 20 GeV/c22

• Jet definition:Jet definition: Corrected ECorrected ETT > 20, | > 20, || < 2.0| < 2.0 JetClu w/ cone R= 0.4JetClu w/ cone R= 0.4 R(e, jet) > 0.52R(e, jet) > 0.52

• Major backgrounds:Major backgrounds: leptonicleptonic (W(W, Z, Zee, WW, Wee, WW, W, tt, tt

multijetmultijet (Fake W signature + jets)(Fake W signature + jets)

CDF collab. PRD 77, 011108(R)

NLO prediction ~ NLO prediction ~ OK (existed up to OK (existed up to

2 jet)2 jet)

MLM : ALPGEN v2.12 (LO) + Herwig v6.5 + MLM + CTEQ5LSMPR: MadGraph v4 (LO) + Pythia v6.3 + CKKW + CTEQ6L1MCFM: NLO, no showering + CTEQ6.1M


WW + Inclusive Jets E + Inclusive Jets ETT SpectraSpectra

• Difficult to simulate. Simplification Difficult to simulate. Simplification strategies:strategies:

Generate 2Generate 22 and use parton shower 2 and use parton shower Generate 2Generate 2N processes but ignore N processes but ignore

virtual corrections (loops)virtual corrections (loops)

• Neither alone is ideal, so hybrid Neither alone is ideal, so hybrid scheme of the two is employedscheme of the two is employed

• Ambiguities ariseAmbiguities arise Possibility for double counting Possibility for double counting ““SMPR” and “MLM” refer to SMPR” and “MLM” refer to

algorithms for removing overlapsalgorithms for removing overlaps• SMPR (CKKW): S.Mrenna, P.Richardson SMPR (CKKW): S.Mrenna, P.Richardson

JHEP, 05(2004) 040JHEP, 05(2004) 040• MLM: J.Alwall et al. arXiv:0706.2569MLM: J.Alwall et al. arXiv:0706.2569

• W+nW+n-jet cross section better -jet cross section better reproduced by SMPR treatment:reproduced by SMPR treatment:

overlap removal or tuned UE in Pythia?overlap removal or tuned UE in Pythia? 3rd

jet

2n

d jet

1st je

t


W+3 jet @ NLO

• Last year calculations @NLO appeared that can be compared to CDF data also for 3 jet events

R.K.Ellis,Melnikov,Zanderighi arXiv:0906.1405

C.F. Berger et al., arXiv:0907.1984


Z/Z/** + Inclusive Jets + Inclusive Jets

• CDF CDF Z /Z /**+jets analysis: +jets analysis: 1.7/fb (electron) 2.4 /fb (muons) 1.7/fb (electron) 2.4 /fb (muons)

• Z /Z /* * selectionselection: seek : seek Z /Z /**ee++ee-- (()) Two ETwo ETT (p (pTT)> 25 GeV leptons)> 25 GeV leptons

66 < M66 < Mℓ ℓℓ ℓ < 116 GeV/c < 116 GeV/c22

At least one At least one ee w/ | w/ || < 1.1, else 1.2 < || < 1.1, else 1.2 < || < 2.8| < 2.8

For muons |For muons ||<1.0|<1.0

• Jet definition:Jet definition: Corrected pCorrected pTT > 30, |y| < 2.1 > 30, |y| < 2.1 MidPoint w/ R=0.7MidPoint w/ R=0.7 R(e, jet) > 0.7R(e, jet) > 0.7

• Major backgrounds: S/B ~ Major backgrounds: S/B ~ 7/17/1 MultijetMultijet WW+jets+jets

CDF collab. PRL 100, 102001 (2008) hep-

ex/0711.3717


Z/Z/** + Inclusive Jets + Inclusive Jets

• CDF CDF Z /Z /**+jets analysis: +jets analysis: 1.7/fb (electron) 2.4 /fb (muons) 1.7/fb (electron) 2.4 /fb (muons)

• Z /Z /* * selectionselection: seek : seek Z Z //**ee++ee-- ( ()) Two ETwo ETT (p (pTT)> 25 GeV leptons)> 25 GeV leptons

66 < M66 < Mℓ ℓℓ ℓ < 116 GeV/c < 116 GeV/c22

At least one At least one ee w/ | w/ || < 1.1, else 1.2 < | < 1.1, else 1.2 < ||| < 2.8| < 2.8

For muons |For muons ||<1.0|<1.0

• Jet definition:Jet definition: Corrected pCorrected pTT > 30, |y| < 2.1 > 30, |y| < 2.1 MidPoint w/ R=0.7MidPoint w/ R=0.7 R(e, jet) > 0.7R(e, jet) > 0.7

• Major backgrounds: S/B ~ Major backgrounds: S/B ~ 7/17/1 MultijetMultijet WW+jets+jets

CDF collab. http://www-cdf.fnal.gov/physics/new/qcd/Zjet

s_mumu2010/index.html

NEW


Z /Z /** + Inclusive Jets + Inclusive Jets

• D0 measure 1D0 measure 1stst, , 22ndnd,3,3rdrd jet p jet pT T spectra spectra

• Compare to MCFM Compare to MCFM pQCD NLO and pQCD NLO and generatorsgenerators

D0 colla

b. Phys

. Lett.

B

678, 45 (2

009),

arXiv.

org:0903.1748

Z+2jet

Z+3jet


WW + + bb-Jets-Jets• CDF CDF W+bW+b-jets analysis-jets analysis: :

1.9/fb1.9/fb

• Goals:Goals: Measure jet cross sectionMeasure jet cross section Compare to theoryCompare to theory Use measurement in backgroundUse measurement in background

estimate for Higgs searchestimate for Higgs search

• WW selection: selection: ppTT > 20 isolated central > 20 isolated central ee or or Missing energy MET > 25 GeVMissing energy MET > 25 GeV

• Jet selection:Jet selection: 1 or 2 corrected E1 or 2 corrected ETT>20 GeV, >20 GeV,

||| < 2.0 JetClu R=0.4 jets| < 2.0 JetClu R=0.4 jets High purity secondary vertex tagHigh purity secondary vertex tag

Page 18

Extract species content Extract species content via via

vertex mass, vertex mass, MMververtt::

CDF collab. arXiv:0909.1505v2

(Submitted to PRL) NEW


• Largest backgrounds: S/B ~ 3/1Largest backgrounds: S/B ~ 3/1 ttbar (40% of total bkgd)ttbar (40% of total bkgd) single top (30%)single top (30%) Fake Fake W W (15%)(15%) WZ WZ (5%)(5%)

• Result: Result:

xxBR = 2.74 BR = 2.74 0.27 0.27 (stat)(stat) 0.42 0.42 (syst) (syst) pbpb

• Predictions: Predictions:

xxBR = 0.78 pbBR = 0.78 pbALPGEN v2.10’ + Pythia v6.325 + MLM + ALPGEN v2.10’ + Pythia v6.325 + MLM + CTEQ6L (CTEQ6L (=M=MWW

22+p+pTWTW22))

xxBR = 1.1 pb (Pythia)BR = 1.1 pb (Pythia)

xxBR = 1.22 BR = 1.22 ±±0.14 pb (NLO – 0.14 pb (NLO – Campbell, Freres-Cordero, Campbell, Freres-Cordero, Reina)Reina)

WW + + b-b-JetsJets

Page 19

This cross section is for b jets from W+b-jet production in events with a high pT central lepton, high pT neutrino and 1 or 2 total jets.

Shape comparisons?NLO comparison?

mismatch by a factor 2 3.5 (~2.9 )Differential measurement with increased statistics underway


ZZ + + b-b-JetsJets

• Similar CDF analysis for Similar CDF analysis for Z+bZ+b-jets: 2/fb-jets: 2/fb

• Utilize Utilize ZZ ee, ee, • Jet definition: Jet definition:

Corrected ECorrected ET T > 20 GeV, |> 20 GeV, || < 1.5| < 1.5 JetClu R=0.7JetClu R=0.7

• Differential cross sections Differential cross sections with comparisons to LO, with comparisons to LO, NLO predictionsNLO predictions

• Pythia ~ OK at low jet ETPythia ~ OK at low jet ET• ALPGEN and MCFM ALPGEN and MCFM

undershoot data in several undershoot data in several bins bins tuning tuning R R improves improves agreementagreement

CDF collab. PRD 77, 011108(R)


Conclusions

• CDF and D0 reached unprecedented precision on W mass and width Legacy measurements that will be further

improved and could challenge the SM• W/Z clean probes for proton PDF

W asymmetry at high lepton ET still an issue

• With multi-fb-1 data set detailed comparison of multi-jet events in association with W/Z NLO pQCD in good shape (exception W+bjet?) Matrix-Element + parton shower MC do a

fairly good job in describing spectra but can be further tuned

BACKUP


MW syst.


CDF 2.1 fb-1 (electron) arXiv:0908.3914

σ = 256.6 ± 0.7(stat.) ± 2.0 (syst.) pb

d/dy(Z/ll)

• Probe low-x PDF through high rapidity Drell-Yan pairs


WW + Inclusive Jets + Inclusive Jets

• Spectra OK up to 4 parton in the final Spectra OK up to 4 parton in the final state, normalization in these plots state, normalization in these plots “ad-hoc” (scaled to the first bin).“ad-hoc” (scaled to the first bin).


Z /Z /** + Inclusive Jets + Inclusive Jets

• NLO predictions NLO predictions for jet pfor jet pTT differential differential cross section cross section are accurateare accurate

• NLO predictions NLO predictions for jet for jet multiplicity also multiplicity also accurateaccurate NLO-to-LO NLO-to-LO

scaling appears scaling appears to be a safe to be a safe thing to do herething to do here


ZZ + + b-b-JetsJets

V+b-Jets Summary:


PDF with Tevatron data


Rare W Decays

W-

W-

Clean final state : enhanced by BSM physics.SM branching fraction : 10-6 - 10-8

Becomes sensitive to new physics with data samples ofseveral million Ws


Rare W Decays

206 candidate events in signal (75 < Mπγ < 85 GeV) region

Predicted background = 219

physics results with w/z from tevatron marco rescigno infn/roma on behalf of cdf and d0 collab....

Documents

rescigno moriond ewk

ewk global fitswz

w production

w asymmetrycompared

w asymmetryphys

w asymmetrycompare d0

anomalous gw

precision lepton momentum