W/Z + Jets in ATLAS. Standard LHC Workshop April 12, 2012 Copenhagen, Denmark

Transcription

1 W/Z Jets in Standard LHC Workshop April, 0 Copenhagen, Denmark Imai Jen- La Plante (University of Chicago) on behalf of the CollaboraLon

2 QCD Studies with W and Z Bosons Studies of produc8on in associa8on with a W or Z boson are key for understanding Standard Model (SM) and beyond SM physics Important teslng ground for perturbalve QCD prediclons Background to other intereslng processes: top, Higgs, SUSY Constrain parton distribulon funclons (PDFs) of the proton DisLncLve leptonic decays and abundant produclon at LHC

3 Cross SecLon Measurement Measure inclusive cross seclons σ(v ) Br(W lν or Z ll), cross seclon ralos σ(v )/σ(v - ), and differenlal cross seclons with respect to p and other observables Use lepton and phase space within the detector acceptance Electron p > 0 GeV, η <.7 excluding.7 < η <.5 Muon p > 0 GeV, η <. W selec8on requires exactly one electron or muon, neutrino p (missing E ) > 5 GeV and transverse mass > 0 GeV Z selec8on requires exactly two oppositely charged electrons or muons, with invariant mass 66 GeV < m ll < 6 GeV Reconstruct s using the an8- k algorithm with distance parameter R=0. Jet rapidity <., p > 0 GeV (also 0 GeV)

4 Backgrounds: W Jets QCD mull background eslmated from data using control sample with reversed lepton seleclon criteria, normalized by fipng missing E before final seleclon (missing E > 5 GeV and transverse mass > 0 GeV) All other processes eslmated from simulalon and normalized to (N)NLO cross seclon prediclons Events / 5 GeV W 0 s Data 0, We QCD W dibosons Zee Z tt single top Ldt=6 pb s=7 ev Events / 5 GeV W 0 s Data 0, W! QCD W dibosons Z!! Z tt single top Ldt=6 pb s=7 ev miss E [GeV] miss E [GeV]

5 Backgrounds: Z Jets QCD mull background eslmated from data using control sample with reversed lepton seleclon criteria, normalized by fipng dilepton invariant mass before final seleclon (66 GeV < m ll < 6 GeV) QCD background less significant in the muon channel Events / 5 GeV L dt = 6 pb, s, R = 0., p y > 0 GeV, <. Data 0 ( s = 7 ev) - Z/*( e e ) s () - Z/*( e e ) s (Sherpa) Multi s WW,WZ,ZZ tt W( e) s Z/*( - ) s Statistical Uncertainties Only Events / 5 GeV L dt = 5 pb, s, R = 0., p y > 0 GeV, <. Data 0 ( s = 7 ev) Z/ *(!! - )s () Z/ *(!! - )s (Sherpa) WW,ZZ,WZ t t Z/ *( - )s Multi s W(!)s Statistical Uncertainties Only m e - e [GeV] [GeV] m! -! 5

6 Uncorrected Jet MulLplicity: W Jets Observed mullpliciles shown before background subtraclon and correclon for detector effects Good agreement between data and prediclons Events 6 5 Ldt=6 pb We s Data 0, We QCD W dibosons Zee Z tt single top s=7 ev Events 6 5 Ldt=6 pb W! s Data 0, W! QCD W dibosons Z!! Z tt single top s=7 ev.0 Data/MC 0 5 Inclusive Jet Multiplicity, 0 5 Inclusive Jet Multiplicity, 6

7 Uncorrected Jet MulLplicity: Z Jets Detector level expectalons for Z s also agree with data Events / bin 5 L dt = 6 pb s, R = 0., p > 0 GeV, y <. Statistical Uncertainties Only Events / bin 5 L dt = 5 pb s, R = 0., p > 0 GeV, y <. Statistical Uncertainties Only 0 0 Data 0 ( s = 7 ev) - Z/*(!! )s () - Z/*(!! )s (Sherpa) WW,ZZ,WZ t t - Z/*( )s Multi s W(!)s 7

8 SystemaLc UncertainLes Dominated by uncertainty on the energy scale (JES) JES uncertainty.5% to %, depending on p and rapidity Fractional Uncertainty Wl s Jet Energy Scale Sum of Other Uncertainties Relative systematic variation Z/*( e e ) s s, R = 0., > 0 GeV, y <. p otal JES, JER Electron Selection Background Unfolding Inclusive Jet Multiplicity, y (leading ) 8

9 Cross SecLon Results ) ) [pb] - e L dt = 6 pb s, R = 0., p > 0 GeV, y <. - Z/*( e e ) s Data 0 ( s = 7 ev) HERWIG Sherpa PYHIA (normalized to data) BlackHat ) ) [pb] -! L dt = 5 pb s, R = 0., p > 0 GeV, y <. - Z/*(!! )s Data 0 ( s = 7 ev) HERWIG Sherpa PYHIA (normalized to data) BlackHat (Z/*( e (Z/*(! Data / NLO.6 Data 0 / BlackHat theoretical uncertainties...6 Data 0 / NNLO uncertainties Data 0 / Sherpa Data / NLO Data 0 / BlackHat theoretical uncertainties Data 0 / NNLO uncertainties Data 0 / Sherpa Results from electron and muon decay channels combined using Best Linear Unbiased EsLmate (BLUE) method 9

10 Cross SecLon Results: W Jets Compare measured cross seclons s) [pb] heory/data (W 0 Ldt=6 pb anti-k s, R=0. p >0 GeV, y <. Wl s Data 0, s=7 ev SHERPA PYHIA BLACKHA-SHERPA 0 Inclusive Jet Multiplicity, σ(w ) Br(W lν) with LO MEPS simulalons, all normalized to NNLO inclusive cross seclon calculated with FEWZ: version. with CEQ6L PDFs and AUE tune SHERPA version.. with CEQ6.6M PDFs and default tune PYHIA ( ) version 6.. with MRS 007 LO PDFs, AMB tune Also compare with NLO pqcd calculalons for up to s from BLACKHA- SHERPA using CEQ6.6M PDFs, renormalizalon and factorizalon scales H /, with non- perturbalve correclons applied

11 Cross SecLon Results: W Jets s) [pb] heory/data (W 0 Ldt=6 pb anti-k s, R=0. p >0 GeV, y <. Wl s Data 0, s=7 ev SHERPA PYHIA BLACKHA-SHERPA 0 Good agreement between data and prediclons, except Pythia Many systemalc uncertainles cancel in ralos of cross seclons: σ(w )/σ(w - ) - s) s) / (W (W Wl s Data 0, s=7 ev SHERPA PYHIA BLACKHA-SHERPA /0 / / / Ldt=6 pb anti-k s, R=0. p >0 GeV, y <. Inclusive Jet Multiplicity, Inclusive Jet Multiplicity Ratio

12 l - l - Cross SecLon Results: Z Jets Data and prediclons also agree for Z s cross seclons and ralos and BLACKHA- SHERPA configured as for W s; SHERPA version.. ) [pb] ) - l (Z( l Data / NLO 5 L dt = 6 pb s, R = 0., p >0 GeV, y <..6 Data 0 / BlackHat. theoretical uncertainties..6 Data 0 /. NNLO uncertainties..6 Data 0 / Sherpa.. - Z/*( l l )s (l=e,! combined) Data 0 ( s = 7eV) HERWIG Sherpa NLO BlackHat CEQ6.6,! = H / ) ) ) / (Z/*( l ) (Z/*( l Data / NLO L dt = 6 pb s, R = 0., p >0 GeV, y <. - Z/*( l l )s (l=e,! combined) Data 0 ( s = 7eV) HERWIG Sherpa NLO BlackHat CEQ6.6,! = H / 0..6 Data 0 / BlackHat. theoretical uncertainties..6 Data 0 /. NNLO uncertainties..6 Data 0 / Sherpa.. /0 / / /

13 DifferenLal Cross SecLons: Jet p Data are well- described by theory prediclons as a funclon of leading p in Z events and second p in Z events [pb/gev] d/dp L dt = 6 pb s, R = 0., p >0 GeV, y <. - Z/*( l l )s (l=e,! combined) Data 0 ( s = 7eV) HERWIG Sherpa NLO BlackHat CEQ6.6,! = H / [pb/gev] d/dp L dt = 6 pb s, R = 0., p >0 GeV, y <. - Z/*( l l )s (l=e,! combined) Data 0 ( s = 7eV) HERWIG Sherpa NLO BlackHat CEQ6.6,! = H / Data / NLO.6 Data 0 / BlackHat theoretical uncertainties.. Data / NLO.6 Data 0 / BlackHat theoretical uncertainties Data 0 / NNLO uncertainties.6.. Data 0 / NNLO uncertainties.6.. Data 0 / Sherpa.6.. Data 0 / Sherpa p (leading ) [GeV] p (nd leading ) [GeV]

14 DifferenLal Cross SecLons: Jet p [pb/gev] d/dp - - Ldt=6 pb W s W s, x W s, x - Wl s Data 0, s=7 ev SHERPA BLACKHA-SHERPA Compare cross seclons with prediclons for W through W s PredicLons describe data well, even p of fourth sub- leading heory/data - -5 W s, x -6 anti-k s, R=0. p >0 GeV, y < W - [pb/gev] d/dp Ldt=6 pb Wl s Data 0, s=7 ev SHERPA BLACKHA-SHERPA anti-k s, R=0. p >0 GeV, y <. heory/data.5 W s First Jet p [GeV] Fourth Jet p [GeV]

15 DifferenLal Cross SecLons: H [pb/gev] d/dh heory/data heory/data Ldt=6 pb W s.5 W W s W s, x - W s, x - W s, x Wl s Data 0, s=7 ev SHERPA BLACKHA-SHERPA anti-k s, R=0. p >0 GeV, y < [GeV] H H, the scalar sum of lepton, neutrino, and p, is a common choice for renormalizalon and factorizalon scales Measure differenlal cross seclons as a funclon of H for W through W s BLACKHA- SHERPA NLO prediclons include matrix elements for one addilonal real emission in each sample prediclons with LO matrix elements for up to 5 partons bexer describe large H, where the contribulon from events with many s is important 5

16 DifferenLal Cross SecLons: H [pb/gev] d/dh Ldt=6 pb W s W s, x Wl s Data 0, s=7 ev SHERPA BLACKHA-SHERPA [pb/gev] d/dh W s Simulation Wl s BLACKHA-SHERPA Modified BLACKHA-SHERPA W s, x - W s, x anti-k s, R=0. p >0 GeV, y <. - heory/data heory/data.5 W W s [GeV] H NLO/ H [GeV] Modified BLACKHA- SHERPA prediclons including matrix elements for addilonal real emissions bexer describe large H 6

17 DifferenLal Cross SecLons: Mass Invariant mass of s of interest for new physics searches PredicLons in good agreement with measured cross seclons d/dm [pb/gev] Wl s Data 0, s=7 ev Ldt=6 pb SHERPA W s BLACKHA-SHERPA - W s, x [pb/gev] jj d / dm L dt = 6 pb s, R = 0., p >0 GeV, y <. - Z/*( l l )s (l=e,! combined) Data 0 ( s = 7eV) HERWIG Sherpa NLO BlackHat CEQ6.6,! = H / heory/data W s, x anti-k s, R=0. p >0 GeV, y <. W Data / NLO -.5 Data 0 / BlackHat theoretical uncertainties.5.5 Data 0 / NNLO uncertainties.5.5 Data 0 / Sherpa jj m (leading, nd leading ) [GeV] m(s) [GeV] 7

18 DifferenLal Cross SecLon: Jet Rapidity Measured cross seclons and NLO pqcd prediclons differ at large rapidity, where PDF sensilvity increases d/dy [pb] 00 Wl s Data 0, s=7 ev SHERPA BLACKHA-SHERPA 50 Ldt=6 pb 0 50 heory/data 0 W anti-k s, R=0. p >0 GeV, y < y(first Jet) 8

19 DifferenLal Cross SecLons: Jet SeparaLon Jet angular differences sensilve to QCD radialon ParLcularly useful distribulons for teslng MEPS simulalons d/dy [pb] 0 Wl s Data 0, s=7 ev 5 SHERPA BLACKHA-SHERPA Ldt=6 pb [pb] d/d Wl s Data 0, s=7 ev SHERPA BLACKHA-SHERPA 0 80 anti-k s, R=0. p >0 GeV, y <. Ldt=6 pb heory/data 5 0 W anti-k s, R=0. p >0 GeV, y < heory/data 0.. W 0 y(first Jet,Second Jet) (First Jet,Second Jet) 9

20 Conclusions W/Z s inclusive and differenlal cross seclon measurements generally well- described by prediclons Agreement between data and LO MEPS simulalons with high mullplicity ME First comparison with NLO pqcd calcula8ons up to W/Z s DifferenLal measurements, especially separalon, provide informalon for further development of MEPS simulalons SHERPA comparison in Ws deviates slightly due to different scales and PDFs Cross sec8ons in HEPDAA and already in use, see e.g., arxiv:.588 [hep- ph] Further details and results for p > 0 GeV available Measurement of the produclon cross seclon for Z/γ* in associalon with s in pp collisions at = 7 ev with the detector, Phys. Rev. D85 (0) 0009 Study of s produced in associalon with a W boson in pp collisions at = 7 ev with the detector, arxiv:.7 More results including W b and Z b at hxps://twiki.cern.ch/twiki/bin/view/ AtlasPublic/StandardModelPublicResults 0