Top Quark Mass Measurements and Decay Properties CDF

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Top Quark Mass Measurements and Decay Properties CDF and DØ collaborations Robert Zitoun Stony

Top Quark Mass Measurements and Decay Properties CDF and DØ collaborations Robert Zitoun Stony Brook and LAPP Outline : 3 new (preliminary) measurements • Mass CDF Run II • Improved mass DØ Run I • W helicity CDF Run I R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

Motivation • • Discovered ~ 8 years ago. Still little known (~100 events +

Motivation • • Discovered ~ 8 years ago. Still little known (~100 events + background) Mass Mt is a basic standard model parameter • Affects observables (LEP/SLD, n. N) through radiative corrections • 2 Ge. V on Mt is worth 10 Me. V on MW • Mt ~ = v√ 2 =175 Ge. V EW symmetry breaking understanding might benefit from study of its decay properties R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

Top Mass: Published Results DØ CDF dilepton 168. 4 ± 12. 3 ± 3.

Top Mass: Published Results DØ CDF dilepton 168. 4 ± 12. 3 ± 3. 6 Ge. V lepton + jets combined 172. 1 ± 5. 2 ± 4. 9 Ge. V 172. 1 ± 7. 1 Ge. V dilepton + jets all hadronic combined 167. 4 ± 10. 3 ± 4. 8 Ge. V 176. 1 ± 5. 3 Ge. V 186. 0 ± 10. 0 ± 5. 7 Ge. V 176. 1 ± 6. 6 Ge. V Tevatron • 174. 3 ± 5. 1 Ge. V statistics background • 2ℓ + 2 jets 5% Z, instrumental • 1ℓ(e/ ) + 4 jets 30% W + 4 jets • 6 jets 45% QCD combinatorics jet energy scale b-tagging reduces background and combinatorics R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

Mt measurement Case of 1ℓ + 4 jets event • 2 -constraint kinematical fit

Mt measurement Case of 1ℓ + 4 jets event • 2 -constraint kinematical fit → Mt • pn unknown – 3 • Impose p. T balance +2 • M(q 1 q 2) = MW +1 • M(ℓn) = MW +1 • M(W+b) = M(W–b) +1 • 4 jets: 12 combinations per event (× 2 depending on kinematics ambiguities) → keep best c 2 • Fit Mt distribution with modeled production and background q 1 q 2 b q W t q R. Zitoun, Stony Brook and LAPP t n W b ℓ CDF Run 1 Moriond 2003, QCD session

CDF Run II Data Mass Measurement ℓ + 4 jets channel R. Zitoun, Stony

CDF Run II Data Mass Measurement ℓ + 4 jets channel R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

Data • Integrated luminosity 72 pb-1 • Event selection (similar to Run I) •

Data • Integrated luminosity 72 pb-1 • Event selection (similar to Run I) • • One isolated high p. T central e or 4 jets ET>15 Ge. V & | |<2. 0 ET>20 Ge. V Z veto Jet 1 Jet 2 Jet 4 µ • muon • electron • photon 33 candidates • Jet 3 Background (~13 events) • • W + 4 jets fake leptons, diboson, Drell-Yan, single top R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

Result CDF preliminary • • • was 4. 4 Ge. V in Run I

Result CDF preliminary • • • was 4. 4 Ge. V in Run I should improve quickly with improved detector understanding Systematics break down R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

Using b-tagging • Reduce background with b-tagging (56 pb-1 only) • • event tagging

Using b-tagging • Reduce background with b-tagging (56 pb-1 only) • • event tagging efficiency = 45 ± 1 ± 5 % (from data + MC) Relax 4 th jet > 8 Ge. V 11 candidates (background ~ 1 event) • Not yet fitted, but looks like a mass peak R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

DØ Run I Data Mass Reanalysis ℓ + 4 jets channel R. Zitoun, Stony

DØ Run I Data Mass Reanalysis ℓ + 4 jets channel R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

 • Outline of the method Kondo’s method (uses full set of event observables)

• Outline of the method Kondo’s method (uses full set of event observables) • Define a signal event probability • Define a background probability i-th event final state • Build an event probability parameters (Mt, c 1, c 2) • Build a likelihood • Minimize to get Mt (c 1 and c 2) R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

Signal and Background • Signal probability • Background probability • Only W + 4

Signal and Background • Signal probability • Background probability • Only W + 4 jets background considered MC signal MC bkg • 80% of total • found adequate to represent multijet background • Calculated with VECBOS • Keep events with Pbkg<10– 11 R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

 • Result DØ Run. I statistics (125 pb– 1) [PRD 58 (1998), 052001]

• Result DØ Run. I statistics (125 pb– 1) [PRD 58 (1998), 052001] • events: 91 → 77 with exactly 4 jets → 22 after prob cut -log(likelihood) vs Mt • likelihood vs Mt Preliminary result: Mt = 179. 9 3. 6 6. 0 Ge. V was 5. 6 Ge. V eq. × 2. 4 increase in stat R. Zitoun, Stony Brook and LAPP next slide Moriond 2003, QCD session

 • • • Systematic Uncertainty Main contribution from jet energy scale Signal model

• • • Systematic Uncertainty Main contribution from jet energy scale Signal model 1. 5 Ge. V Jet Energy Scale 5. 6 Ge. V Background model 1. 0 Ge. V Parton Distribution Function 0. 2 Ge. V Noise and multiple interactions PRD 58 52001, (1998) 1. 3 Ge. V Acceptance Correction 0. 5 Ge. V Improvement in systematics coming soon Further improvement by controlling the W→jj mass -log(likelihood) vs MW R. Zitoun, Stony Brook and LAPP likelihood vs MW Moriond 2003, QCD session

CDF Run I Data W helicity in top decay R. Zitoun, Stony Brook and

CDF Run I Data W helicity in top decay R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

Top quark Decay • In V–A theory, top produces no h = +1 W;

Top quark Decay • In V–A theory, top produces no h = +1 W; only • h = 0: 70% t • h = – 1: 30% b n W+ yℓ * ℓ+ • Angle accessible through associated mass M 2ℓb = ½ (M 2 t – M 2 W)(1 + cosy*ℓ) R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

New CDF W helicity study (Run I) • Use dilepton and lepton+jets events with

New CDF W helicity study (Run I) • Use dilepton and lepton+jets events with 1 and 2 SVX b-tagged jets) • Preliminary (f = 0 in SM; f = 1 if all V+A) y ar in lim f. V+A= – 0. 21+0. 42– 0. 25 ± 0. 21 • F CD n Ru I e Pr Expect ± 0. 1 stat± 0. 1 syst with 2 fb-1 R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

 • Run II Outlook • • Run II with 2 fb– 1 (~2005)

• Run II Outlook • • Run II with 2 fb– 1 (~2005) • 14000 top events produced per expt • O(500) ℓ + jets with b-tagging. Improvements to Mt • Increased statistics × 20 • New method (× 2. 5) • Improved b-tagging (CDF increased acceptance, DØ lifetime tag) • Better understanding of jet energy scale (W→jj helps) • Better knowledge of ISR/FSR • DMt ~ 2 -3 Ge. V / expt Rare decays cg , cg, c. Z, H+b |Vtb| (single top x-section) • Is top playing a special role in the breaking of electroweak symmetry? • R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

Summary • • • Mass from Run II (CDF) 171. 2 ± 13. 4

Summary • • • Mass from Run II (CDF) 171. 2 ± 13. 4 ± 9. 9 Ge. V SV m- Improved mass from Run I (DØ) 179. 9 ± 3. 6 ± 6. 0 Ge. V IP Jet 2 W helicity from Run I (CDF) f. V+A= – 0. 21+0. 42– 0. 25 ± 0. 21 Jet 1 IP SV R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

 • Top production and decay ~5 pb cross section (7 pb @ 1.

• Top production and decay ~5 pb cross section (7 pb @ 1. 96 Te. V) q 6 jets 45% e/ + 4 jets 15% each 2ℓ + 2 jets ~1% each ~35% with t • 2 b jets b q W p t t p b n W l R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

Fermilab Tevatron • • Main Injector (150 Ge. V) has replaced Main Ring pbar

Fermilab Tevatron • • Main Injector (150 Ge. V) has replaced Main Ring pbar recycler? ? √s = 1. 8→ 1. 96 Te. V • increases 35% Run IIa • goal 8. 6× 1031 cm-2 s-1 (× 5) • 2 fb-1 by 2004 -05 (× 20) 160 pb– 1 4 pb– 1 week– 1 3× 1031 cm– 2 s– 1 Jan 2002 ↓ ↑ Jan 2003 DØ Booster p Tevatron p CDF source R. Zitoun, Stony Brook and LAPP Main Injector & Recycler Moriond 2003, QCD session

 • • DØ Run I Mass Reanalysis (ℓ + jets) New method Use

• • DØ Run I Mass Reanalysis (ℓ + jets) New method Use of full set of event observables through likelihood allows unnormalized P parameters (Mt, . . . ) • i-th event final state • integration over n + incident parton momenta (5 dim) Real life issues: • Acceptance • Final state parton momenta not really observed x = e– and jets x = e– and partons transfer function from partons to jets R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session

 • • • Technicalities For each event, probability is an integral over 5

• • • Technicalities For each event, probability is an integral over 5 variables • 20 variables (2 in + 6× 3 final) • 4 constraints (E, p conservation) • 11 measures (3 pe + 8 partons) • optimized choice : Mt, Mtbar, m. W–, m. W+, E 1(1 jet) 12 undistiguishable parton configurations: sum 12 probabilities W(x, y) probability of measuring x when y was produced in the collision • Monte Carlo used to compute Wjet (different for q and b’s) • Parametrized as the sum of 2 gaussians (E-dependent parameters) x = e– and jets x = e– and partons transfer function from partons to jets R. Zitoun, Stony Brook and LAPP Moriond 2003, QCD session