Γ W. (GeV) 3. τ e universality in W decays

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1 UCR/DØ/99-22 FERMILAB-CONF-99/39-E W and Z Proprtis at th Tvatron arxiv:hp-x/99137v1 18 Oct Introduction John Ellison (for th CDF and DØ Collaborations) Dpartmnt of Physics, Univrsity of California, Rivrsid, CA johnllison@ucrdu Abstract W prsnt rcntrsults from CDF and DØ on W and Z production crosssctions, th width of th W boson, τ univrsality in W dcays, trilinar gaug boson couplings, and on th obsrvation of Z b b In this papr w rviw som rcnt rsults on W and Z proprtis obtaind by th CDF and DØ collaborations at th Frmilab Tvatron Th rsults ar basd on data sts collctd during th run ( Run 1b ), with total intgratd luminositisof 85 9pb 1 prxprimnt CDF (DØ) obsrvd 41,666 (67,78) W ν candidat vnts and 5,152 (5,397) Z + candidats 2 Masurmnt of th Ratio of W ν and Z + Cross Sctions Nw rsults on th W and Z production cross sctions tims lctronic branching ratios from CDF and DØ ar shown in Fig 1 DØ masur [1] σ W B(W ν) = 231±1 (stat) ±5 (syst) ± 1 (lum) pb and σ Z B(Z + ) = 221 ± 3 (stat) ± 4 (syst) ± 1 (lum) pb, whr lum is du to th uncrtainty on th intgratd luminosity CDF obtain σ Z B(Z + ) = 249 ± 5 (stat syst) ± 1 (lum) pb and σ Z B(Z + ) = 237 ± 9 (stat lum) ± 9 (lum) pb [2] Th rrors ar dominatd by th uncrtainty in th intgratd luminosity of th data sampls Th DØ and CDF rsults must b compard with car, sinc th xprimnts us diffrnt total p p cross sctions to dtrmin thir intgratd luminositis CDFusthirownmasurmnt,whilDØtakth avrag of th CDF, E71 and E811 masurmnts As a rsult thr is a scal factor which must b Papr prsntd at th Intrnational Europhysics Confrnc on High Enrgy Physics, Tampr, Finland, July, 1999 σ W B (nb) σ Z B (nb) DØ W lν Z l + l - Data st: 92/93 94/96 s = 18 GV CDF τ O(α s 2) Thory (van Nrvn t al) 92/93 94/96 Figur 1 Masurmnts of th W ν and Z + cross sctions from DØ and CDF applid to th masurd cross sctions: g if using th CDF normalization, th DØ Run 1b cross sctions must b multiplid by 162 Not that th rsults in Fig 1 hav not bn rscald Th intgratd luminosity uncrtainty and many of th othr systmatic rrors cancl in th ratio of cross sctions R = σ W B(W ν)/σ Z B(Z + ) This allows indirct, prcis masurmnts of th W ν branching fraction and th width of th W boson This follows using σ W B(W ν) σ Z B(Z + ) = σ W 1 Γ(W ν) σ Z B(Z + ) Γ(W) togthr with th thortical calculation of

2 2 ALEPH SM Dirct: SM L DELPHI OPAL L DELPHI OPAL CDF (Prliminary) Prliminary: CDF+DØ Indirct: CDF+DØ (Prliminary) B(W ν) (%) Figur 2 Masurmnts of B(W ν) σ W /σ Z [3], th masurd Z + branching ratio from LEP [4], and th SM valu of Γ(W ν) [5] Th masurd valus of R ar R = 149 ± 14 (stat) ± 21 (syst) for DØ and R = 138 ± 14(stat)±17(syst) for CDF, using th combind lctron data from Runs 1a and 1b Th main sourcs of systmatic rrors ar du to uncrtaintis in backgrounds, fficincis, and lctron nrgy scal A 1% rror du to NLO lctrowak radiativ corrctions is also includd Th two R masurmnts hav bn combind, yilding R = 142 ± 18 Using this combind valu of R, th rsulting branching fraction is B(W ν) = (143 ± 25)% and th width of th W boson is dtrmind to b Γ(W) = 2171 ± 52 GV Th rsults agr with th SM prdictions whn th rrors ar takn into account, as shown in Figs 2 and 3 A significant sourc of systmatic rror (15%) ariss from th thortical uncrtainty on σ W /σ Z du to th choic of rnormalizationschm and lctrowak radiativ corrctions Not that at prsnt th rrors du to thortical uncrtaintis on B(W ν) and Γ(W) ar largr than th statistical uncrtainty A dirct masurmnt of th W boson width is possibl using a fit to transvrs mass ( ) spctrum in W vnts Th W width dirctly affcts th shap of th distribution, most prominntly at high valus of, whr th Brit-Wignr lin shap dominats ovr dtctor rsolution ffcts CDF hav nw prliminary rsults for Run 1b W ν and W ν vnts, using a binnd liklihood fit in th rgion > 1 GV/c 2 Th Γ W (GV) Figur 3 Dirct and indirct masurmnts of th W boson width W vnts ar modld using a similar simulation to that usd in th W mass analyss [6] This mthod is lss modl-dpndnt than th indirct masurmnt discussd abov, but with th currnt data sts it is statistically limitd Th transvrs mass fits ar shown in Figs 4 and 5 Th rsults ar Γ(W) = 217±125 (stat)±15 (syst) GV from th lctron data and Γ(W) = 178 ± 195 (stat) ± 135 (syst) GV from th muon data Ths rsults ar combind with th Run 1a lctron masurmnt, yilding Γ(W) = 255 ± 1 (stat) ± 75 (syst) GV This rsult is consistnt with th SM prdiction, as shown in Fig 3 3 τ univrsality in W dcays DØ hav updatd thir prliminary masurmnt of th W cross sction tims W τν branching ratio using Run 1b data and th nw luminosity normalization, and obtain σ W B(W τν) = 222 ± 9 (stat) ± 1 (syst) ± 1 (lum) pb Th ratio of this quantity to th corrsponding lctron-channl quantity masurs th ratio of th lctrowak chargd currnt couplings, g W τ /gw DØ masur g W τ /g W = 98±3, to b compard with th arlir CDF rsult of g W τ /g W = 97±7 using Run 1a data, and th prliminary CDF rsult g W τ /g W = 11±19 which uss Run 1b data, but is obtaind from an analysis basd on th diffrnc in lctron impact paramtr distributions in W τν ννν and W ν vnts Ths rsults ar shown in Fig 6

3 3 vnts / GV 2 1 CDF(1B) Prliminary Γ W = 2175 ± 165 GV (stat+syst) UA1 UA2 vnts / 2GV -2 log(l) vs Γ W (,ν) (GV) vnts shown (149 ± 17 bkg) 438 with 1< <2 GV 211 with 11< <2 GV 7 with >2 GV (,ν) (GV) CDF 1a CDF 1b DØ 1b Avrag Figur 4 CDF dirct masurmnt of th W boson width using a fit to th ν transvrs mass # Evnts # Evnts CDF(1B) Prliminary Γ W = GV Τ W (,ν) (GV) v in fit rgion 1 2 (1 < < 2) v in normalisation rgion (5 < < 2) 1 1 Backgrounds (,ν) (GV) Figur 5 CDF dirct masurmnt of th W width using a fit to th ν transvrs mass 4 Updatd DØ rsults on trilinar gaug boson couplings DØ hav rcntly publishd limits on th trilinar gaug boson couplings from p p W W/W Z νjj vnts [7] Thy us a liklihood fit to th p T (ν) spctrum, which is snsitiv to non-sm couplings Anomalous couplings would rsult in an nhancmnt of vnts at high p T (ν) No such nhancmnt is sn and DØ obtain 95% confidnc lvl limits, assuming qual WWγ and WWZ couplings (i λ γ = λ Z and κ γ = κ Z ) using a dipol form factor with form factor scal -2 log(l) Figur 6 Masurmnts of g W τ /g W Λ FF = 2 TV: 52 < λ < 54 and 62 < κ < 88 DØ hav also sarchd for W Z vnts in th ν and ν channls [7] On vnt passs th slction critria, an ν candidat, shown in Fig 7 For both channls combind, th SM prdiction is 245 ± 154 vnts, with an stimatd background of 5 ± 15 vnts In th absnc of an xcss of vnts, which would b an indication of non-sm WWZ couplings, DØ st limits on anomalous couplings This analysis is most snsitiv to th couplings λ and g1 Z, with rsulting limits λ < 142 and g Z 1 < 163 at th 95% CL, using a form factor scal of 1 TV Bcaus W Z production is snsitiv only to th W W Z coupling, ths rsults ar indpndnt of any assumptions about th WWγ coupling Th nw rsults on th trilinar gaug boson couplings hav bn combind with prvious rsults from DØ to yild nw global limits from DØ utilizing all diboson production analyss Figur 8 shows th rsults for th couplings κ and λ Th DØ rsults us a form factor scal of 2 TV, and thrfor, th LEP rrors should b scald by a factor of (1 + s/λ FF ) 2 whn comparing with DØ Hr, s is th LEP cm nrgy This is not don in Fig 8, sinc th ffct only amounts to a fw prcnt incras As can b sn, th DØ rsults ar comparabl to thos from th LEP xprimnts, and bcaus of th diffrnt production mchanisms and ffcts of anomalous couplings, th rsults ar complmntary

4 4 CAL+TKS END VIEW 15-MAY :27 Run Evnt MAR :54 Max ET = 516 GV MISS ET(3)= 48 GV ETA(MIN:-25-MAX: 25) EM2 EM3 M T (2)=747 GV M13=936 GV Miss Et EM ICD+MG HAD MISS ET EM1 MUON ELEC TAUS VEES OTHER Figur 7 End viwofthdøcalorimtr andtracking systms showing a candidat WZ ν dcay Evnts pr 1 GV/c CDF PRELIMINARY Excss ovr background Expctd MC shap (PYTHIA) Obsrvd vnts Prdictd bgr Dijt Mass (GV/c 2 ) Dijt Invariant Mass (GV/c 2 ) Figur 9 CDF Z b b invariant mass plot Th figur shows th dijt invariant mass for vnts containing a cntral muon and two SVX-taggd jts Evnts pr 1 GV/c prliminary ALEPH DELPHI L OPAL LEP D +1 1 LEP+D χ 2 /N dof =148/ λ γ prliminary ALEPH DELPHI L OPAL LEP D LEP+D κ γ χ 2 /N dof =28/4 Figur 8 Masurmnts of th trilinar gaug boson coupling paramtrs λ and κ from DØ and LEP 5 CDF obsrvation of Z b b Th Z b b dcay channl, copious at LEP and SLC, is challnging to obsrv at th Tvatron du to th larg QCD dijt background Howvr, it is an important bnchmark signal for futur physics at th Tvatron it can b usd to improv th jt rsolution in Higgs sarchs involving th H b b dcay, and it will b an important calibration tool for th top quark mass masurmnt In th CDF analysis, smi-lptonic dcays of th b-quark ar utilizd by slcting vnts from a sampl collctd with a cntral muon triggr Offlin, a good muon candidat with p T > 75 GV is rquird, togthr with two jts containing chargd tracks forming a wllidntifid, displacd scondary vrtx in th Silicon Vrtx Dtctor Topological cuts ar applid to rjct QCD background, basd on th amount and topology of th radiation surrounding th two lading jts Figur 9 shows th backgroundsubtractd dijt invariant mass distribution Th pak and width of th distribution ar as xpctd from Mont Carlo Z b b signal Accounting for th systmatic uncrtainty on th background prdiction (4%), th significanc of th xcss ovr background is 32 standard dviations Rfrncs

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