Top quark pair production measurements using the ATLAS detector at the LHC

Transcription

1 op quark pair production meaurement uing the ALAS detector at the LHC Ki Lie on behalf of the ALAS Collaboration Univerity of Illinoi at Urbana-Champaign Phenomenology 25 May 5th, 25 K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th / 2

2 op Quark Phyic Dicovered at evatron in 995 PRL 74, 2626 / PRL 74, with urpriingly large ma m top m(gold atom) m top cloe to electroweak ymmetry breaking cale Larget Yukawa coupling to Higg: y t and very hort lifetime Decay before hadronizing Allow acce of bare quark from decay product Production rate and other propertie tet the Standard Model Background to Higg production and poibly new phyic If new phyic i there, poible direct/indirect coupling to top A window to new phyic K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 2 / 2

3 op quark pair production t t produced via trong interaction at the LHC, mainly by gluon fuion heory QCD preciion: NNLO+NNLL oft gluon reummation Decay channel: σ pp t t(7 ev) = 77 + σ pp t t(8 ev) = pb 5 pb (at m top =72.5 ) Czakon, Mitov, Fiedler, PRL (23) 2524 K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 3 / 2

4 Incluive t t cro ection at 7eV and 8eV: eµ Event Eur.Phy.J. C74 (24) 39 MC/ ALAS - = 8 ev, 2.3 fb 22 Powheg+PY Wt Z+jet Diboon Mi-ID lepton Powheg+PY MC@NLO+HW Alpgen+HW 2 3 N b-tag he mot precie reult in ALAS Require: oppoite-charge eµ; 4.6fb at 7eV, 2.3fb at 8eV Event with one or two b-tagged jet Simultaneou determination of σ t t and b-jet recontruction efficiency to minimize ytematic uncertaintie Alo extract m pole top and et limit on direct top pair production σ t t = 82.9 ± 3.(tat) ± 4.2(yt) ± 3.6(lumi) ± 3.3(beam)pb( = 7 ev) σ t t = ±.7(tat) ± 5.5(yt) ± 7.5(lumi) ± 4.2(beam)pb( = 8 ev) Good agreement with QCD NNLO+NNLL calculation K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 4 / 2

5 Incluive t t cro ection at 8eV: l+jet, 2.3fb arxiv:54.425: Submied Require: l+jet, l=e or µ Ue a likelihood dicriminant variable built from lepton η l and tranformed aplanarity A emplate fit to binned likelihood dicriminant in data Sytematic dominated by t t MC modeling Fiducial σ fid t t i alo meaured Event /.25 / Expectation 3 25 ALAS - Ldt = 2.3 fb e+ 3 jet = 8 ev V+Jet Multijet Single op Diboon η e Event /.5 / Expectation 3 ALAS - Ldt = 2.3 fb 3 µ+ 3 jet = 8 ev V+Jet Multijet Single op Diboon A' σ t t = 26 ± (tat) +2 2 (yt) ± 8(lumi) ± 4.(beam)pb K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 5 / 2

6 Summary of incluive t t cro ection All σ t t meaurement agree well with theory prediction cro ection [pb] Incluive evatron combined*.96 ev (L=8.8 fb ) - ALAS dilepton 7 ev (L=4.6 fb ) - CMS dilepton 7 ev (L=2.3 fb ) - ALAS l+jet* 7 ev (L=.7 fb ) - CMS l+jet 7 ev (L=2.3 fb ) - ALAS dilepton 8 ev (L=2.3 fb ) - CMS dilepton 8 ev (L=5.3 fb ) - LHC combined eµ* 8 ev (L= fb ) - ALAS l+jet* 8 ev (L=5.8 fb ) - CMS l+jet* 8 ev (L=2.8 fb ) * Preliminary NNLO+NNLL (pp) ALAS+CMS Preliminary OPLHCWG Sep 24 NNLO+NNLL (pp) Czakon, Fiedler, Mitov, PRL (23) 2524 m top = 72.5, PDF α uncertaintie according to PDF4LHC S [ev] K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 6 / 2

7 t Differential meaurement at 7eV: reolved top (l+jet) Phy. Rev. D 9, 724 Normalized t t differential cro ection meaurement a a function of p t and m t t, p t t and y t t unfolded to top parton, full phae pace LO and NLO MC generally harder than data, increaing with p i ofter than both QCD NLO and NLO+NNLL calculation in high p t and high m t t alo compared to variou NLO PDF uing MCFM (LO) HERAPDF.5 bet decribe data in high p t and m t t Main ytematic: JES, JER, I/FSR, PS, MC modeling - σ dp MC heory / ALAS - = 7 ev MC@NLO+HERWIG POWHEG+HERWIG POWHEG+PYHIA p t [] ALAS - Ldt = 4.6 fb = 7 ev CNLO MSW28NLO NNPDF 2.3 HERAPDF m [] K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 7 / 2

8 Differential meaurement at 7eV: peudo top (l+jet) arxiv: : Submied Novel t t differential cro ection meaurement uing peudo-top ˆt ˆt: top-proxy recontructed from detector-level or particle-level object fiducial meaurement minimize modeling dependence a a function of pˆt and yˆt of leptonic and hadronic peudo-top; and of peudo-top pair mˆt ˆt ytem pˆt ˆt, yˆt ˆt Similar concluion to parton level ditribution, with lower total uncertaintie pb fid dm(t l t h ) ALAS = 7 ev, 4.6 fb tat. yt. uncert. POWHEG+PYHIA POWHEG+HERWIG POWHEG(HERAPDF)+PYHIA MC@NLO+HERWIG Main ytematic: b-tagging, JES, I/FSR, PS, MC modeling Expected/ m(t l t h ) [] K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 8 / 2

9 t Differential meaurement at 8eV: booted top (l+jet) ALAS-CONF Firt booted top pair differential cro ection meaurement a a function of hadronic top p, with p > 3 Jet ubtructure technique uing anti-k t jet with R=. Meaured at fiducial particle level and full phae-pace parton level LO and NLO MC generally harder than data, increaing with p HERAPDF with limited hard radiation (h damp ) bet decribe data Preciion gained in particle level ditribution [fb/] t ()/dp MC / ALAS Preliminary 2.3 fb, = 8 ev ALPGEN + HERWIG MC@NLO + HERWIG POWHEG + HERWIG POWHEG + PYHIA top quark p [] [fb/] ()/dp MC / POWHEG + PYHIA C + hdamp = ALAS Preliminary 2.3 fb, = 8 ev C + hdamp = m top HERAPDF + hdamp = HERAPDF + hdamp = m top Particle top jet candidate p [] Main ytematic: large-r JES, ignal modeling (at parton-level) K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 9 / 2

10 t t+jet meaurement at 7eV (l+jet, 4.6fb ) JHEP(25)2 t t differential cro ection a a function of jet multiplicity and jet p Several jet p threhold Senitivity to PS modeling at high jet multiplicitie Compared to LO and NLO MC POWHEG+PYHIA with limited hard radiation (h damp ): MC bet decribe data MC@NLO+HERWIG: predict too few event at high jet multiplicitie Main ytematic: JES, b-tagging, I/FSR [pb] /dn jet Expected/ anti k t R=.4 η < 2.5 p > 25 l+jet ALAS POWHEG+PYHIA POWHEG(h )+PYHIA damp MC@NLO+HERWIG ALPGEN+PYHIA (α Down) - = 7 ev n jet K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th / 2

11 t t + γ and t t+v, V=W or Z meaurement Phy Rev D (25) 7eV: photon E > 2, l+jet; 4.59fb Oberved number of event and fiducial cro ection meaurement Obervation of t tγ: 5.3σ σ fid xbr in agreement with NLO prediction t tγ ALAS-CONF eV: 2l (SS), 2l (OS), 3l; 2.3fb Meaured ignal trength of t tz and t tw Evidence of t tz and t tw : 4.9σ µ t tw,z conitent with NLO QCD calculation Event/ 2 ALAS - =7 ev, L dt = 4.59 fb Muon channel Signal γ background Hadron fake otal uncertainty from fit σ / σ SM (Z) 2.5 ALAS Preliminary ALAS Bet Fit - L dt = 2.3 fb = 8 ev ALAS 68% CL ALAS 95% CL NLO calculation* Z heory uncertainty W heory uncertainty * Campbell(22),Kardo(2),Garzelli(2,22) p [] io σ / σ SM (W) K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th / 2

12 Concluion op quark pair production meaurement in ALAS have reached preciion level that put the SM to tet. he mot precie meaurement in incluive t t cro ection i more precie than theoretical preciion. Differential meaurement of t t production in top p and other kinematic provide contraint to improve MC modeling and parameter tuning in t t production. Meaurement of t t production in aociation with gauge boon are conitent with the SM. With new technique for electing high-p top pair, ALAS i ready for more top phyic in the ev regime. K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 2 / 2

13 Extra lide K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 2 / 2

14 ALAS op public reult All reult hown can be found in the following page: hp://twiki.cern.ch/twiki/bin/view/atlapublic/oppublicreult K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 2 / 2

15 Differential t t cro ection meaurement Booted top (8eV) and reolved top (7eV) Unfolding to particle level (in fiducial region) and parton level (extrapolated to full phae pace) A a function of kinematic propertie of t and t t Compared to LO and NLO MC generator Compared to NLO QCD calculation [] top jet candidate p ALAS Simulation Preliminary particle top jet candidate p [] POWHEG + PYHIA = 8 ev [] particle top jet candidate p ALAS Simulation Preliminary = 8 ev top quark p [] POWHEG + PYHIA ALAS-CONF K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 2 / 2

16 σ σ σ t σ Comparion to MC and PDF Phy. Rev. D 9, 724 MC: - dp -3 MC@NLO+HERWIG POWHEG+HERWIG - dm -3 MC@NLO+HERWIG POWHEG+HERWIG - dp -2-3 MC@NLO+HERWIG POWHEG+HERWIG d y MC@NLO+HERWIG POWHEG+HERWIG POWHEG+PYHIA POWHEG+PYHIA POWHEG+PYHIA POWHEG+PYHIA -4-4 ALAS - = 7 ev -5 ALAS - = 7 ev -4-5 ALAS - = 7 ev - ALAS - = 7 ev MC p t [] MC m [] MC p [] MC y PDF: heory / ALAS - Ldt = 4.6 fb = 7 ev CNLO MSW28NLO NNPDF 2.3 HERAPDF t p [] heory / ALAS - Ldt = 4.6 fb = 7 ev CNLO MSW28NLO NNPDF 2.3 HERAPDF m [] heory / ALAS - Ldt = 4.6 fb = 7 ev CNLO MSW28NLO NNPDF 2.3 HERAPDF p [] heory /.4 ALAS CNLO - MSW28NLO.3 Ldt = 4.6 fb NNPDF 2.3 HERAPDF.5 = 7 ev y K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 2 / 2

17 Comparion to MC LO arxiv: : Submied pb fid (t h ) dp 2 ALAS = 7 ev, 4.6 fb tat. yt. uncert. ALPGEN+PYHIA ALPGEN+PYHIA (α ALPGEN+PYHIA (α UP) DOWN) pb fid (t l ) dp 2 ALAS = 7 ev, 4.6 fb tat. yt. uncert. ALPGEN+PYHIA ALPGEN+PYHIA (α ALPGEN+PYHIA (α UP) DOWN) pb fid d y(t h ) ALAS = 7 ev, 4.6 fb tat. yt. uncert. ALPGEN+PYHIA ALPGEN+PYHIA (α ALPGEN+PYHIA (α UP) DOWN) pb fid d y(t l ) ALAS = 7 ev, 4.6 fb tat. yt. uncert. ALPGEN+PYHIA ALPGEN+PYHIA (α ALPGEN+PYHIA (α UP) DOWN) Expected/ p (t h ) [] Expected/ p (t l ) [] Expected/ y(t h ) Expected/ y(t l ) pb fid dp(t t l h ) 2 ALAS = 7 ev, 4.6 fb tat. yt. uncert. ALPGEN+PYHIA ALPGEN+PYHIA (α ALPGEN+PYHIA (α UP) DOWN) pb fid d y(t t l h ) ALAS = 7 ev, 4.6 fb tat. yt. uncert. ALPGEN+PYHIA ALPGEN+PYHIA (α ALPGEN+PYHIA (α UP) DOWN) pb fid dm(t t l h ) 2 3 ALAS = 7 ev, 4.6 fb tat. yt. uncert. ALPGEN+PYHIA ALPGEN+PYHIA (α ALPGEN+PYHIA (α UP) DOWN) 3 4 Expected/ p (t l t h ) [] Expected/ y(t l t h ) Expected/ m(t l t h ) [] K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 2 / 2

18 t t t t σ σ σ t σ σ σ t σ Comparion to NLO QCD calculation Phy. Rev. D 9, 724, ALAS-CONF dp -3 ALAS NLO QCD - = 7 ev - dm -3-4 ALAS NLO QCD - = 7 ev - dp -2-3 ALAS NLO QCD - = 7 ev d y ALAS NLO QCD - = 7 ev NLO p t [] NLO m [] NLO p [] NLO y - dp -3 ALAS NLO+NNLL - = 7 ev - dm -3-4 ALAS NLO+NNLL - = 7 ev - dp ALAS NLO+NNLL - = 7 ev NLO+NNLL p t [] NLO+NNLL m [] NLO+NNLL p [] [fb/] ()/dp MC / POWHEG + PYHIA POWHEG + PYHIA + EWK ALAS Preliminary ALAS Preliminary ALAS Preliminary ALAS Preliminary fb, = 8 ev 2.3 fb, = 8 ev fb, = 8 ev 2.3 fb, = 8 ev Particle top jet candidate p [] [fb/] ()/dp MC / 2.5 POWHEG + PYHIA POWHEG + PYHIA + EWK top quark p [] [fb/] ()/dp MC / POWHEG + PYHIA C + hdamp =.5 C + hdamp = m top HERAPDF + hdamp = HERAPDF + hdamp = m top Particle top jet candidate p [] [fb/] ()/dp MC / 2.5 POWHEG + PYHIA C + hdamp = C + hdamp = m top HERAPDF + hdamp = HERAPDF + hdamp = m top top quark p [] K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 2 / 2

19 t t + γ meaurement at 7eV: l+jet Phy Rev D (25) Require: photon with E > 2, l+jet; 4.59fb Obervation + fiducial cro ection meaurement Extract fiducial cro ection by template fit to the photon track iolation ditribution p io Obervation of t tγ: 5.3σ (σt tγ fid xbr=63±8(tat.)+7 3 (yt.)±(lumi.)fb) Meaurement in agreement with NLO prediction Event/ 2 ALAS - =7 ev, L dt = 4.59 fb Muon channel Signal γ background Hadron fake otal uncertainty from fit ALAS - =7 ev, L dt = 4.59 fb Electron channel heoretical uncertainty (tat.) (yt.) ± (lumi.) fb 7 Muon channel (tat.) (yt.) ± (lumi.) fb Combined 63 ± 8 (tat.) +7 3 (yt.) ± (lumi.) fb heoretical prediction 48 ± fb p [] io σ BR [fb] γ K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 2 / 2

20 t t+v, V=W or Z meaurement at 8eV ALAS-CONF Search in 3 channel: 2l (SS), 2l (OS), 3l; 2.3fb Firt evidence of t tz, t tw : t tv, 4.9σ exce over bkg, µ t tv = Simultaneou meaurement of t tz and t tw ignal trength: µ t tz = , µ t tw = , overall ignificance: 3.σ for both t tz and t tw Meaurement conitent with NLO QCD calculation Event 3 ALAS Preliminary L = 2.3 fb = 8 ev Z W ZZ WZ Other H tz MiID lepton σ / σ SM (Z) 2.5 ALAS Preliminary ALAS Bet Fit - L dt = 2.3 fb = 8 ev ALAS 68% CL ALAS 95% CL NLO calculation* Z heory uncertainty W heory uncertainty 5 /Pred 2.5 * Campbell(22),Kardo(2),Garzelli(2,22) SRZbj4 SRZb2j3 SRZb2j4 SRWL3 SR2µ SS σ / σ SM (W) K. Lie (Univ. of Illinoi) op quark pair production in ALAS Pheno 25, May 5th 2 / 2