NuTeV. CDF TeVatron. Main Injector

Transcription

1 Electroweak Physics at the TeVatron Kevin McFarland University of Rochester RADCOR-2 Carmel-by-the-Sea, California 11 September 2

2 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 2 NuTeV CDF TeVatron D Main Injector 1. Introduction, Goals, Musings 2. On-Shell Physics ffl W Properties ffl Multi-Boson Final States 3. Off-Shell Physics ffl NuTeV sin 2 W ffl Drell-Yan 4. Discovering a Higgs 5. Conclusions

3 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 3 Status of TeVatron Where s CDF? Cosmic in COT, Calorimeter

4 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 4 Status of TeVatron (cont'd) ffl TeVatron has achieved pp collisions with Main Injector. p s = 196 GeV. L ο 1 27, c.f. design L of ffl CDF being installed for (short) commissioning" run ffl CDF/D to be ready for beam by March 1, 21. or else" ffl Initial running with 36 bunch operation in machine. Occupancy a concern Average Number of Interactions per Crossing E E+31 6 Bunches 36 Bunches 18 Bunches Luminosity E+32 design lum E+33. Hope for quick transition to 99 bunch operation, ffit = 132 ns

5 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 5 Status of Precision Electroweak Measurements: A Three Hour Tour? A dozen years ago... ffl The basic structure of the electroweak Standard Model appeared correct. Low-energy measurements of fl Z interference and Z exchange. Crude boson masses ffl Time was ripe for a quick BIG SURPRISE. Fat Z?. Generation dependence in couplings?. Physics at TeV mass scales appearing in precision measurements?. Other ffl Who ordered this?. Certainly not an experimentalist!

6 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 6 Status of Precision Electroweak Measurements (cont'd) Osaka 2 Measurement Pull Pull m Z [GeV] ±.21.5 Γ Z [GeV] ± σ hadr [nb] ± R l ± A,l fb.1714 ± A e.1498 ± A τ.1439 ± sin 2 θ lept eff.2321 ±.1.7 m W [GeV] ± R b ± R c.179 ± A,b fb.99 ± A,c fb.689 ± A b.922 ± A c.631 ± sin 2 θ lept eff.2398 ± sin 2 θ W.2255 ± m W [GeV] ± m t [GeV] ± α (5) had (m Z ).284 ± (Figure courtesy of LEP EWWG)

7 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 7 Status of Precision Electroweak Measurements (cont'd) 6 4 theory uncertainty α (5) α had =.284± ±.46 χ 2 2 Excluded Preliminary m H [GeV] (Figure courtesy of LEP EWWG)

8 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 8 Struggling to Find New Physics Where, if anywhere in the precision data, are there indications for deviations from Standard Model expectations in the precision data that would guide us as we begin to search again at the TeVatron? ffl sin 2 eff; leptons W vs sin 2 ffl Also ff had eff; quarks W 1 3 Preliminary A,l fb.2399 ±.53 A τ ±.53 A e ±.61 A,b fb ±.36 A,c fb ±.82 <Q fb >.2321 ±.1 Average(LEP) ±.23 χ 2 /d.o.f.: 5.7 / 5 A l (SLD).2398 ±.26 Average(LEP+SLD) ±.17 χ 2 /d.o.f.: 11.9 / 6 m H [GeV] sin 2 θ lept eff α (5) had =.284 ±.65 α s =.119 ±.2 m t = ± 5.1 GeV ffl Atomic Parity Violation ( 137 Cs)

9 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 9 Atomic Parity Violation fl Z Interference e e Z, γ ffl Interaction suppressed by q 2 =M 2 Z ffl But not in forbidden (6S $ 7S) transitions (parity-violating) ffl Magnitude of interference (parity-violating) relative to fl-exchange gives hq W i = hq EM i (light quarks) Recent 137 Cs APV measurement Bennett,S.C. and Wieman,C.E. PRL 82, (1999) Q W = 72:6 ± :28(exp) ± :34(theory) Q SM W = 73:9 ± :3 I believe our sigmas mean a bit more than the sigmas that you use [in particle physics]." Carl Wieman, at an FNAL Seminar

10 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 1 On-Shell or Off-Shell? ffl LEP Z pole data disfavors most new physics in the weak neutral current itself ffl However, this constraint still allows for new physics in offshell processes l l q Z Pure Z exchange l ffl New interactions can't strongly affect Z pole ffl E.g., Z exchange, unmixed q Z Z q Z Z Z-Z Mixing ffl Global fit shows some Z-Z mixing allowed. ο 1 3 weakly favored? Langacker and Erler, PRL 84, (2)

11 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 11 On-Shell (W Properties) p _ p W,Z, γ l l, ν ffl W production is dominant source of high p t leptons at TeVatron ff(pp! W ) BR(W! `ν) ff(pp! Z) BR(Z! ``) ß 1 ffl Drell-Yan extends to very high mass `+` pairs ffl Generally clean, obvious" sample number of events D W e ν candidates p T (e) (GeV)

12 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 12 W Mass ffl ff, G F, M Z ) M W at tree level ffl M W measurement probes radiative corrections t h? W W W W W W b M W α M 2 T W M W α ln M H? New Physics. Constraint on Higgs mass. Key consistency check for model M W (GeV/c 2 ) TEVATRON LEP Higgs Mass (GeV/c 2 ) LEP1,SLD,νN data M W -M top contours : 68% CL M top (GeV/c 2 ) ff Mtop = 5:1 GeV, ff MW = 63 MeV

13 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 13 W Mass (cont'd) CDF/D Technique: lepton ffl Infer neutrino transverse kinematics from ~p ν T = ~u T ~ p`t ν # Events ffl Form m T = u T r 2p`Tp ν T (1 cos(ffi` ffi ν )) ffl Select events with high p`t (25 or 3 GeV) and low u T (below 15 or 2 GeV). CDF,D: central, fi `fi < 1. D: endcap e, 1:5 < fi `fi < 2:5 (ο 3% of sample). ß events per experiment ffl Fit m T to extract m W (D fits p`t and pν t CDF(1B) Preliminary W eν Fit region as well) χ 2 /df = 82.6/7 (5 < M T < 12) χ 2 /df = 32.4/35 (65 < M T < 1) Mw = /-.65 (stat) GeV Backgrounds KS(prob) = 16% Transverse Mass (GeV) # Events CDF(1B) Preliminary W µν Fit region χ 2 /df = 147/131 (5 < M T < 12) χ 2 /df = 6.6/7 (65 < M T < 1) Mw = /-.1 (stat) GeV Backgrounds KS(prob) = 21% Transverse Mass (GeV)

14 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 14 W Mass (cont'd) Systematics: p`t measurement ffl Primary control from Z! `+` data 25 CDF(1B) Preliminary CDF(1B) Preliminary Z ee χ 2 25 /df=1.3 Z µµ χ 2 /df= E/p Residuals:DATA-MC CDF(1B) Preliminary Mw = 34 +/- 17 MeV W Z E T (GeV) : W+Z events ffl Attempt to cross-check this with E=p determination in CDF 1B electron data failed by 4ff, ( M Z ο 5 MeV) ffl Highlights difficulty of measurement ffl ffim W ο 7 85 MeV (Run I) Systematics: Recoil Model ffl Response of detectors to underlying event ffl Measured (again) in Z! `+` data ffl ffim W ο 3 4 MeV (Run I)

15 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 15 W Mass (cont'd) Systematics: dff=dy ffl Direct effect on lineshape in fit Well constrained from W charge asymmetry Charge Asymmetry MRS-R1(MOD) MRS-R1 MRS-T MRS-T(MOD) d/u : Variation for Mw analysis MRS-R2 MRS-R2(MOD) Lepton Rapidity ffl ffim W ο 1 2 MeV (Run I) Systematics: Scaling for Run II ffl Most systematics now directly constrained from W;Z data ) statistically limited ffl Anticipate ff MW of 2 4 MeV from first 2fb 1 (early 23?) from CDF/D ffl Control of theoretical systematics also key see talk by D.Wackeroth

16 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 16 W Width ffl TeVatron high statistics W sample ideal for study of W properties ffl Run II (2 fb 1 per experiment), expect 1 6 W ffl W lineshape as a measure of W CDF Preliminary Transverse mass lineshape (normalized to unit area) for Γ W =1.5,1.7,...,2.5 GeV events / GeV events / 2GeV # Events # Events ffl High m T dominated by Breit- Wigner, not resolution 2 1 CDF(1B) Preliminary Γ W = ±.165 GeV (stat+syst) -2 log(l) vs Γ W M T (e,ν) (GeV) events shown (149 ± 17 bkg) 438 with 1<M T <2 GeV 211 with 11<M T <2 GeV 7 with M T >2 GeV CDF(1B) Preliminary Γ W = GeV M T (e,ν) (GeV) Τ W M T (µ,ν) (GeV) ev. in fit region 1 2 (1 < M T < 2) ev. in normalisation region (5 < M T < 2) 1 1 Backgrounds M T (µ,ν) (GeV) -2 log(l) CDF W = 2:55 ± :1 ± :75 LEP Preliminary : Summer ALEPH 2.17±.2 DELPHI 2.9±.15 L3 2.19±.21 OPAL 2.4±.18 LEP 2.12±.11 CDF Γ W [GeV] Run II (2 fb 1 ), ff W ß 2 4 MeV M T (e,ν) (GeV)

17 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 17 W /Z Production ffl W, Z boson production also is a clean way to probe proton constituents p x 1 l _ p x 2 W,Z l, ν ffl M V = p x 1 x 2 s ffl Role in precision measurements. e.g., W mass and W asymmetry Charge Asymmetry MRS-R1(MOD) MRS-R1 MRS-T MRS-T(MOD) d/u : Variation for Mw analysis MRS-R2 MRS-R2(MOD) Lepton Rapidity

18 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 18 dσ(γ * /Z)/dy (pb) W /Z Production (cont'd) CDF e + e - χ 2 /ndof LO(CTEQ5L), 33.3/27 NLO(MRST99), 23.1/27 NLO(CTEQ5M-1), 24.3/27 x 1 =M Z e y s -1/2 x 2 =M Z e -y s -1/ y x 1 x 2 66< M γ*/z < 116 GeV/c 2 Forward e ± reconstruction key for these measurements Silicon tracking and EM calorimetry only! (a) εa r.45.4 CC,CP,CF,PP,PF CC,CP,CF CC y m COT END WALL HADRON CAL SVX II 5 LAYERS CDF Tracking Volume SOLENOID INTERMEDIATE SILICON LAYERS END PLUG EM CALORIMETER n = 1. END PLUG HADRON CALORIMETER 3 n = 2. n = 3. 3 m

19 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 19 Gauge Boson Couplings ffl Standard Model allows for non-zero trilinear Gauge boson couplings. WWfl, WWZ allowed. ZZfl, Zflfl, ZZZ zero at tree level ffl Search for non-standard couplings to probe structure of physics beyond Standard Model ffl Multi-boson signatures clean if W;Z! leptons. again, waiting increased L CAL+TKS END VIEW 15-MAY :27 Run Event MAR :54 Max ET = 51.6 GeV MISS ET(3)= 4.8 GeV ETA(MIN:-25-MAX: 25) Miss. Et EM ICD+MG HAD MISS ET EM EM1 MUON ELEC TAUS VEES EM3 OTHER M T (2)=74.7 GeV M13=93.6 GeV Run I D WZ candidate!

20 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 2 Gauge Boson Couplings (cont'd) preliminary ALEPH DELPHI L OPAL LEP D LEP+D χ 2 /N dof = 2.8/4 - lnl κ γ preliminary ALEPH DELPHI L OPAL LEP D LEP+D χ 2 /N dof = 1.48/4 - lnl λ γ ffl Expect scaling with p L (or better) ffl WZ signature unique to hadron colliders

21 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 21 Off-Shell: NuTeV SSQT Sign Selected Quadrupole Train NuTeV Wrong-Sign Protons DUMPED DUMPED Right-Sign ACCEPTED π,κ π,κ Event Length ν µ ff NC q W q ff CC + sin 2 νn W Event Length ν Z ν q q Short (NC) Events Long (CC) Events R 2 Short=Long ν 386K 919K :4198 ± :8(stat) ν 88.7K 21K :4215 ± :17(stat)

22 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 22 PRELIMINARY NuTeV sin 2 W NuTeV measures: sin 2 W (on shell) = :2253 ± :19(stat) ± :1(syst) sin 2 (on shell) W 1 M W 2 M Z 2 ffl The most precise νn measurement of the weak mixing angle / / / / / / /-.64 UA2 CDF* D* ALEPH* DELPHI* L3* OPAL* ffl Precision comparable to collider measurements /-.38 World Average /-.11 * : Preliminary NuTeV* Mw (GeV)

23 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 23 NuTeV sin 2 W (cont'd) R = ffν NC ffnc ν ffcc ν ffcc ν B@ sin2 W CA = = u 2 L + d2 L u 2 R d 2 R NuTeV measurement! constraint on the Z -quark couplings: :453 sin 2 W = :2277 ± :22 = :8587u 2 L + :8828d2 L 1:1657u2 R 1:2288d2 R.4 g 2 L;R = u2 L;R + d2 L;R NuTeV R constraint: :68 ± :6 =.3 SM :6134 u L + :9972 u R 2:631 d L :5261 d R APV constraint: (Q exp W Q SM W )=QSM W = :14 ± :6 = + 5:1436( u L + u R ) + 5:7729( d L + d R ) 2 g e A

24 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 24 Extra Z Bosons? ffl Several authors have suggested E(6) Z natural interpretation of APV data as the most. Rosner, Casalbuoni et al, unmixed Z. Erler and Langacker, general case ffl APV, NuTeV (and pp Drell-Yan) all sensitive to direct Z exchange (interference) 95% Confidence Level Lower Mass Limits on Z ': Z = Z χ cosfi + Z ψ sinfi NuTeV Limits (mixing=-1 3 ) mz χ 675 GeV at 95% CL mz 38 GeV at 95% CL Rosner hep-ph/ Casalbuoni, et al. hep-ph/1215

25 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 25 High Mass Drell-Yan ffl Search for highest mass `±` ffl Sensitive to ``qq contact interactions, Z ψ D Run I e + e sample ffl Sample is clean, fertile ground for new physics Events Comparison of the data with the SM predictions DØ (2) Run I, 127 pb -1 Dielectrons and diphotons E T (EM) > 45 GeV η < 1.1 or 1.5 < η < 2.5 F/M S, 4 TeV Limits on Large Spatial Extra Dimensions 95% CL Upper Limit on F/M S 4 n = 2, M S > 1.37 TeV n = 3, M S > 1.44 TeV n = 4, M S > 1.21 TeV n = 5, M S > 1.1 TeV n = 6, M S > 1.2 TeV n = 7, M S >.97 TeV Instrumental background SM.3 F = 2/(n-2), n > 2 M S F = 2log( ), n = 2.6 TeV (after Han et al. PRD 59 (1999) 156) M(EM-EM), GeV.2 DØ (2) M S, TeV

26 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 26 High Mass Drell-Yan (cont'd) p _ p W,Z, γ l l, ν ffl Off-shell, forward-backward asymmetry is large ffl Assume Standard Model behavior on Z pole; probe high-mass region and therefore interference ffl CDF new result in process; enhanced angular coverage using forward events!

27 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 27 High Mass Drell-Yan (cont'd) ffl Forward e ± defined by EM calorimeter... ffl...in conjunction with silicon stub. charge determination! r cal p T min φ cal p T max y ffl Probing off-shell (interference) key for Z searches! ffl fl Λ =Z Λ =Z Λ interference is signature of Z ffl Differentiates among E(6) Z possibilities ffl Just awaiting L::: (Rosner, Phys. Rev. D54 178)

28 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 28 Standard Model Higgs ffl Discovery of the Higgs would complete the experimental verification of the electroweak Standard Model ffl SM Higgs: Decay. Single doublet of scalar fields. Predicts couplings but not Higgs mass ffl For 9 < M H < 13 GeV, BR(H! b μ b) varies between.85 and.6. ffl At M H > 14 GeV, H! WW Λ dominates 9 13 Production at TeVatron 1 2 σ(pp _ H+X) [pb] ffl VH production provides additional handle for 1 gg H s = 2 TeV M t = 175 GeV CTEQ4M background rejection. 1 ffl ff(wh)=ff(zh) ß 1:6 1-1 qq Hqq qq _ HW ffl gg! H, H! bb hopeless at TeVatron qq _ HZ gg,qq _ Htt _ gg,qq _ Hbb _ M H [GeV]

29 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 29 CDF Run I Searches No signal observed! WH! `ν b μ b Expect : 3 ± 5 1-tag, 6: ± :6 2-tag Observe : 36 1-tag, 6 2-tag V H! qqb μ b Expect : 6 2-tag events Observe : tag events Events / (1 GeV) 2 Entries 5 Data (5 events) Total background (3.2 events) ZZ + tt + mistags only Dijet Mass (GeV) ZH! `+` b μ b Expect : 3:2 ± :7 1-tag Observe : 5 ZH! ννb μ b Expect : 39:2 ± 4:4 1-tag, 3:9 ± :6 2-tag Observe : 4 1-tag, 4 2-tag

30 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 3 CDF Run I Searches (cont'd) σ(pp VH )β CDF 95% C.L. σβ (pb) 1 2 CDF PRELIMINARY VH qq bb VH lν bb combined (lν, qq ) 1 VH νν bb combined : VH l + l - / νν bb 1 standard model Higgs Mass (GeV/c 2 ) ffl Limits ο 5 SM expectations with :1 fb 1 ffl 2 fb 1 is still not enough

31 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 31 Run II Prospects χ theory uncertainty α (5) had =.284± ±.46 ffl Precision data strongly suggest that Higgs is below 19 GeV ffl Suggests opportunity at TeVatron with high luminosity ffl Two mass ranges: Excluded Preliminary m H [GeV] M H < 13 GeV V H `νbb, ννbb, `+` bb. M H < 13 GeV H! bb. M H > 13 GeV H! WW Λ M H > 13 GeV V H and gg `+`+jj, `+`+`, `+` Events per 1 GeV/c Events per 1 GeV/c 2 1 Excess over background Expected MC shape (PYTHIA) Observed events Predicted bgr Dijet Mass (GeV/c 2 ) Low backgrounds make analysis viable, even with low cross-sections and low branching ratios into leptons Dijet Invariant Mass (GeV/c 2 )

32 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 32 Run II Prospects Run 2B Run 2 (Run II Higgs Working Group, All VH Channels and gg! H; H! WW Λ ) ffl With 2 fb 1 can probe M H up to ο 115 GeV/c 2. ffl Need ο 2 fb 1 for a 3ff signal for M H to 18 GeV ffl Prospects for luminosity beyond 15 fb 1 are unclear before LHC

33 Kevin McFarland, RADCOR-2, Electroweak Physics at the TeVatron 33 Conclusions The TeVatron is Poised for a Long Run! ffl The Signature" for Run II is W /Z! `(ν=`). 1 6 W by 23!. Precision measurements: W mass and width. Using W as a tool: parton distributions, luminosity calibration for TeVatron. Multi-boson production ffl The targets" for New Physics in Run II (2 fb 1 ). Z (testing Wieman's sigma" calibration). Weak couplings of top (Willenbrock's talk) ffl Standard Model Higgs. Requires 1 2 fb 1 to get in the game. TeVatron is a tough place to study a 114:9 GeV Higgs (just to pick a random number). Good news: broad range of masses accessible!. More good news: H! WW Λ clean