Top Quark Properties Measurements with the ATLAS Experiment

Transcription

1 Top Quark Properties Measurements with the ATLAS Experiment Javier Murillo - On Behalf of the ATLAS Top Groups XV Mexican Workshop on Particles and Fields Mazatlán, México November 5, 2015 jamkoons@gmail.com Top Quark Properties 1 / 28

2 Overview 1 Sources of useful information 2 The LHC accelerator and the ATLAS detector 3 Introduction to Top Quark Physics 4 Recent Measurements of Top Quark Properties 5 Progress with LHC Run-II 6 Outlook jamkoons@gmail.com Top Quark Properties 2 / 28

3 Sources of useful information Some sources of useful information European Physical Society HEP 2015 Conference Indico Website Timetable and talks here TOP2015 8th International Workshop on Top Quark Physics Timetable and talks here 50th Rencontres de Moriond EW 2015 Timetable and talks here 37th International Conference on High Energy Physics Timetable and talks here ATLAS Experiment Public Results Summary plots and publications here Top Quark Properties 3 / 28

4 The LHC accelerator and the ATLAS detector The LHC Experiments Main Experiments Incorporated to the LHC Top Quark Properties 4 / 28

5 The LHC accelerator and the ATLAS detector The ATLAS Experiment The ATLAS Detector - Run-I at jamkoons@gmail.com s = 7 TeV, 8 TeV successfully completed Top Quark Properties 5 / 28

6 The LHC accelerator and the ATLAS detector Recent Mesurements Recent Results From ATLAS - Confirming predictive power of the SM Standard Model Total Production Cross Section Measurements Status: March 2015 σ [pb] µb 1 ATLAS Preliminary Run 1 s = 7, 8 TeV pb 1 LHC pp s = 7 TeV Theory LHC pp s = 8 TeV Theory pb 1 Observed fb 1 Observed 20.3 fb total 2.0 fb fb 1 VBF 1 VH t th 10 1 pp total W total Z total t t total t t chan WW+WZ WW total total total H total Wt total WZ total ZZ total t tw total t tz total jamkoons@gmail.com Top Quark Properties 6 / 28

7 The LHC accelerator and the ATLAS detector Recent Mesurements Measurement of the Higgs Mass - arxiv: [hep-ex] The H γγ and H 4l channels are analyzed by fitting the peaks of reconstructed Higgs-boson invariant mass With m H known all the properties of the SM Higgs boson, such as its production cross section and partial decay width, can be predicted Measured masses from the two channels and both experiments are combined, giving a value equal to m H = ± 0.21 (stat.) ± 0.11 (syst.) GeV Likelihood scan for m H measurement Combination of ATLAS and CMS Run-I measurements jamkoons@gmail.com Top Quark Properties 7 / 28

8 1 The LHC accelerator and the ATLAS detector 1 1 b 1 1 q, g q q q g g g g g g g g g g g t1 t1 t1 t1 g g ντ q, g g g g t1 t1 Recent Mesurements [GeV] m χ 0 Lower Limits for Supersymmetry The ATLAS collaboration has performed a wide range of direct searches for supersymmetry during Run-I of the LHC No significant excess of events over the SM expectation is observed Exclusion limits at 95% confidence level have been set for the masses of supersymmetric particles: squarks, gluinos, electroweakinos, sleptons and heavy neutral higgs bosons Excluded limits for neutralino and s-top ~ ~ ~ t t t b f f χ production, ATLAS 0 b f f χ 1 W b 0 χ 1 ~ 0 t 1 t χ 1 ~ 0 t 1 t χ ~ 1 0 t 1 W b χ /b f f 1 ~ 0 t 1 W b χ ~ 1 0 t 1 c χ 1 ~ 0 t 1 b f f χ 1 ~ m( t, χ 0 ) < 0 1 c 0 χ 1 ~ m( t 0 χ 1,χ 0 ) < m 1 / ~ t c χ m W m( / ~ t W b χ s=8 TeV, 20 fb t0l/t1l combined t2l, SC WW t1l, t2l tc tc, t1l ~ t,t) < m 1 χ 0 ~ t t χ Observed limits Expected limits All limits at 95% CL / [GeV] m χ [GeV] m~ t 1 Inclusive Searches 3 rd gen. g med. 3 rd gen. squarks direct production EW direct Long-lived particles RPV Excluded Mass Ranges for SUSY Particles ATLAS SUSY Searches* - 95% CL Lower Limits ATLAS Preliminary Status: July 2015 Model e,µ,τ,γ Jets E miss s = 7, 8 TeV Ldt[fb 1 ] T Mass limit s = 7 TeV s = 8 TeV Reference MSUGRA/CMSSM 0-3 e,µ/1-2τ 2-10 jets/3b Yes TeV m( q)=m( g) q q, q q χ jets Yes GeV m( χ 0 1)=0 GeV, m(1 st gen. q)=m(2 nd gen. q) q q, q q χ 0 1 (compressed) mono-jet 1-3 jets Yes GeV m( q)-m( χ 0 1)<10 GeV q q, q q(ll/lν/νν) χ e,µ (off-z) 2 jets Yes GeV m( χ 0 1)=0 GeV g g, g q q χ jets Yes TeV m( χ 0 1)=0 GeV g g, g qq χ ± 1 qqw ± χ e,µ 2-6 jets Yes TeV m( χ 0 1)<300 GeV, m( χ ± )=0.5(m( χ 0 1)+m( g)) g g, g qq(ll/lν/νν) χ 0 2 e,µ jets TeV m( χ 0 1)=0 GeV GMSB ( l NLSP) 1-2τ+0-1l 0-2 jets Yes TeV tanβ> GGM (bino NLSP) 2γ - Yes TeV cτ(nlsp)<0.1 mm GGM (higgsino-bino NLSP) γ 1 b Yes TeV m( χ 0 1)<900 GeV, cτ(nlsp)<0.1 mm,µ< GGM (higgsino-bino NLSP) γ 2 jets Yes TeV m( χ 0 1)<850 GeV, cτ(nlsp)<0.1 mm,µ> GGM (higgsino NLSP) 2 e,µ (Z) 2 jets Yes 20.3 g 850 GeV m(nlsp)>430 GeV Gravitino LSP 0 mono-jet Yes 20.3 F 1/2 scale 865 GeV m( G)> ev, m( g)=m( q)=1.5 TeV g g, g b b χ b Yes TeV m( χ 0 1)<400 GeV g g, g t t χ jets Yes TeV m( χ 0 1)<350 GeV g g, g t t χ e,µ 1 3 b Yes TeV m( χ 0 1)<400 GeV g g, g b t χ e,µ 3 b Yes TeV m( χ 0 1)<300 GeV b1 b1, b1 b χ b Yes 20.1 b GeV m( χ 0 1)<90 GeV b1 b1, b1 t χ± 1 2 e,µ (SS) 0-3 b Yes 20.3 b GeV m( χ ± 1 )=2 m( χ 0 1) t1 t1, t1 b χ± e,µ 1-2 b Yes 4.7/ GeV GeV m( χ ± 1 ) = 2m( χ 0 1), m( χ 0 1)=55 GeV , t1 t1, t1 Wb χ0 1 or t χ e,µ 0-2 jets/1-2b 1 Yes GeV GeV m( χ 0 1)=1 GeV t1 t1, t1 c χ0 1 0 mono-jet/c-tag Yes GeV m( t1)-m( χ 0 1)<85 GeV t1 t1(natural GMSB) 2 e,µ (Z) 1 b Yes GeV m( χ0 1)>150 GeV t2 t2, t2 t1+z 3 e,µ (Z) 1 b Yes 20.3 t GeV m( χ0 1)<200 GeV ll,r ll,r, l l χ0 1 2 e,µ 0 Yes 20.3 l GeV m( χ 0 1)=0 GeV χ + 1 χ 1, χ + 1 lν(l ν) 2 e,µ 0 Yes 20.3 χ ± GeV m( χ 0 1)=0 GeV, m( l, ν)=0.5(m( χ ± 1 )+m( χ 0 1 1)) χ + 1 χ 1, χ + 1 τν(τ ν) 2τ - Yes 20.3 χ ± GeV m( χ 0 1)=0 GeV, m( τ, ν)=0.5(m( χ ± 1 )+m( χ 0 1 1)) χ ± 1 χ0 2 llν lll( νν),l ν lll( νν) 3 e,µ 0 Yes 20.3 χ ± 700 GeV m( χ ± 1 )=m( χ 0 2), m( χ 0 1)=0, m( l, ν)=0.5(m( χ ± 1 )+m( χ 0 1)) , χ0 2 χ ± 1 χ0 2 W χ 0 1Z χ e,µ 0-2 jets 1 Yes 20.3 χ ± 420 GeV m( χ ± 1 )=m( χ 0 2), m( χ 0 1)=0, sleptons decoupled , , χ0 2 χ ± 1 χ0 2 W χ 0 1h χ 0 1, h b b/ww/ττ/γγ e,µ,γ 0-2 b Yes 20.3 χ ± 250 GeV m( χ ± 1 )=m( χ 0 2), m( χ 0 1)=0, sleptons decoupled , χ0 2 χ 0 2 χ0 3, χ 0 2,3 lrl 4 e,µ 0 Yes 20.3 χ GeV m( χ 0 2)=m( χ 0 3), m( χ 0 1)=0, m( l, ν)=0.5(m( χ 0 2)+m( χ 0 2,3 1)) GGM (wino NLSP) weak prod. 1 e,µ +γ - Yes 20.3 W GeV cτ<1 mm Direct χ + 1 χ 1 prod., long-lived χ ± 1 Disapp. trk 1 jet Yes 20.3 χ ± m( χ ± 1 )-m( χ 0 1) 160 MeV,τ( χ ± GeV 1)=0.2 ns Direct χ + 1 χ 1 prod., long-lived χ ± 1 de/dx trk - Yes 18.4 χ ± m( χ ± 1 )-m( χ 0 1) 160 MeV,τ( χ ± GeV 1)<15 ns Stable, stopped g R-hadron jets Yes GeV m( χ 0 1)=100 GeV, 10µs<τ( g)<1000 s Stable g R-hadron trk TeV GMSB, stable τ, χ 0 1 τ(ẽ, µ)+τ(e,µ) 1-2µ χ GeV 10<tanβ< GMSB, χ 0 1 γ G, long-lived χ 0 2γ - 1 Yes 20.3 χ GeV 2<τ( χ 0 1)<3 ns, SPS8 model g g, χ 0 1 eeν/eµν/µµν displ. ee/eµ/µµ χ TeV 7<cτ( χ 0 1)< 740 mm, m( g)=1.3 TeV GGM g g, χ 0 1 Z G displ. vtx + jets χ TeV 6<cτ( χ 0 1)< 480 mm, m( g)=1.1 TeV LFV pp ντ+ X, ντ eµ/eτ/µτ eµ,eτ,µτ TeV λ 311 =0.11,λ132/133/233= Bilinear RPV CMSSM 2 e,µ (SS) 0-3 b Yes TeV m( q)=m( g), cτlsp<1 mm χ + 1 χ 1, χ + 1 W χ 0 1, χ 0 1 ee νµ,eµ νe 4 e,µ - Yes 20.3 χ ± m( χ 0 1)>0.2 m( χ ± GeV 1 ),λ χ + 1 χ 1, χ + 1 W χ 0 1, χ 0 3 e,µ +τ - 1 ττ νe,eτ ντ Yes 20.3 χ ± m( χ 0 1)>0.2 m( χ ± GeV 1 ),λ g g, g qqq jets GeV BR(t)=BR(b)=BR(c)=0% g g, g q χ 0 1, χ 0 1 qqq jets GeV m( χ 0 1)=600 GeV g g, g t1t, t1 bs 2 e,µ (SS) 0-3 b Yes GeV t1 t1, t1 bs 0 2 jets + 2 b GeV ATLAS-CONF t1 t1, t1 bl 2 e,µ 2 b TeV BR( t1 be/µ)>20% ATLAS-CONF Other Scalar charm, c c χ m~ t 1 [GeV] c Yes 20.3 c 490 GeV m( χ 0 1)<200 GeV Mass scale [TeV] *Only a selection of the available mass limits on new states or phenomena is shown. All limits quoted are observed minus 1σ theoretical signal cross section uncertainty. jamkoons@gmail.com Top Quark Properties 8 / 28

9 Introduction to Top Quark Physics Top Quark Features Why is the top quark so important? The top quark is the heaviest known fundamental particle, m top GeV Precise measurements of m top provide critical input to fits of global electroweak parameters, that help assess the consistency of the SM Higgs-boson mass m H ( 125 GeV), W-boson mass m W ( 80 GeV), and the top quark mass (m top) can be used to directly test the consistency of the SM Measurements of the top quark properties play an important role in testing the Standard Model (SM), of particle physics and its possible extensions jamkoons@gmail.com Top Quark Properties 9 / 28

10 Introduction to Top Quark Physics Top Quark Features Events with top quark t t pairs: l + jets, dilepton and all-hadronic channels At the LHC, top quarks are produced mainly in pairs via the strong interaction and are predicted to decay via the electroweak interaction into a W-boson and a bottom quark with nearly 100% branching fraction Diagram illustrating an l + jets event / Image by T. Wengler, TOP2012 jamkoons@gmail.com Top Quark Properties 10 / 28

11 Recent Measurements of Top Quark Properties Measurement of the spin correlation in t t decays jamkoons@gmail.com Top Quark Properties / 28

12 Recent Measurements of Top Quark Properties Spin Correlation Measurement of the Spin Correlation - arxiv: [hep-ex] Correlation between the top and antitop quarks spins is extracted from dilepton t t events using full data from proton-proton collisions recorded at s = 8 TeV The degree of spin correlation is defined as A helicity = N like N unlike N like +N unlike A binned log-likelihood fit is used to extract the spin correlation from the φ distribution in data f SM = 1.20 ± 0.05 (stat.) ± 0.13 (syst.) GeV Signal Diagram Event Selection Yields jamkoons@gmail.com Top Quark Properties 11 / 28

13 Recent Measurements of Top Quark Properties Spin Correlation Measurement of the Spin Correlation - arxiv: [hep-ex] A search is performed for top squarks decaying predominantly to top quarks and light neutralinos Top squarks with masses between the top quark mass ( GeV) and 191 GeV are excluded at 95 % C.L. Selected data events with MC templates Lower limit on stop mass at 95 % C.L. jamkoons@gmail.com Top Quark Properties 12 / 28

14 Recent Measurements of Top Quark Properties Charge Asymmetry Measurement of charge asymmetry in t t decays jamkoons@gmail.com Top Quark Properties / 28

15 Recent Measurements of Top Quark Properties Charge Asymmetry Measurement of Charge Asymmetry - arxiv: [hep-ex] Measurement of the t t production charge asymmetry gluon-gluon fusion q q annihilation l + jets channel A likelihood fit is used to reconstruct the t t system ( ) Rapidity y = 1ln E+p z 2 E p z y = y top y antitop difference between the absolute value of the top quark rapidity y t and the absolute value of the top antiquark rapidity y t A C = N( y >0) N( y <0) N( y >0)+N( y <0) A bayesian unfolding procedure is used to obtain asymmetry at parton level y Distributions jamkoons@gmail.com Top Quark Properties 13 / 28

16 Recent Measurements of Top Quark Properties Charge Asymmetry Measurement of Charge Asymmetry - arxiv: [hep-ex] The precision of the measurement is limited by the statistical uncertainty For differential measurements it is not possible to distinguish between the SM and Beyond the SM (BSM) models at this level of precision ATLAS and CMS measurements on A C are compared with the t t forward-backward asymmetry A FB measured by the Tevatron by CDF and D0 experiments so far the measured values for both asymmetries by four different experiments agree with the SM predictions SM Prediction & Measurements jamkoons@gmail.com Top Quark Properties 14 / 28

17 Recent Measurements of Top Quark Properties Charge Asymmetry Measurement of the color flow in t t decays jamkoons@gmail.com Top Quark Properties / 28

18 Recent Measurements of Top Quark Properties Color Flow Measurement of Color Flow in t t events - arxiv: [hep-ex] The distribution and orientation of energy inside jets is predicted to be an experimental handle on color connections between hard-scatter quarks and gluons initiating jets Color Flow Models Previous studies by D0 experiment arxiv: [hep-ex] Jet coordinates (y J, φ J ) Jet component i, position r i = ( y i, φ i ) Pull Angle Pull vector v J p = i J pt i r i r p T J i Pull angle θ p(j 1, J 2) is expected to be sensitive to color connections between the jets If two jets originate from color connected quarks θ p 0 jamkoons@gmail.com Top Quark Properties 15 / 28

19 Recent Measurements of Top Quark Properties Color Flow Measurement of Color Flow in t t events - arxiv: [hep-ex] A similar unfolding technique is used as with charge asymmetry measurements Comparison with models with simulated W-bosons that are color charged (color octet W-boson) or color neutral χ 2 test statistic is used for comparison with the SM and flipped models Data differ from flipped model by 2.3σ and 3.3σ with just charged particles Pull Angle Distribution (l + jets channel) Pull Angle Distribution (l + jets channel) jamkoons@gmail.com Top Quark Properties 16 / 28

20 Recent Measurements of Top Quark Properties Color Flow Measurement of the W-boson polarization in t t decays jamkoons@gmail.com Top Quark Properties / 28

21 Recent Measurements of Top Quark Properties W-boson Polarization W-boson polarization in t t events - arxiv: [hep-ex] Polarisation fractions are predicted at next-to-next-to-leading-order (NNLO), QCD calculations are predicted to be: F o = ± 0.005, F L = ± and F R = ± These fractions are measured using the distribution of the angular variable cosθ, where θ is the angle between the direction of momentum of lepton and the corresponding b-quark 1 N dn dcos θ = 3 4 sin2 θ F (1 cos θ ) 2 F L (1 + cos θ ) 2 F R Analytical Templates Detector Level Templates jamkoons@gmail.com Top Quark Properties 17 / 28

22 Recent Measurements of Top Quark Properties W-boson Polarization W-boson polarization in t t events - arxiv: [hep-ex] Previous measurements performed by CDF and D0 collaborations are in agreement with the SM predictions In the presence of anomalous Wtb couplings the helicity fractions and angular asymmetries depart from their SM values The measured values are: F 0 = 0.67 ± 0.07, F L = 0.32 ± 0.04 and F R = 0.01 ± 0.05 Fit with data Overall Combination jamkoons@gmail.com Top Quark Properties 18 / 28

23 Recent Measurements of Top Quark Properties Top Quark Mass Measurement of the top quark mass in t t decays jamkoons@gmail.com Top Quark Properties / 28

24 Recent Measurements of Top Quark Properties Top Quark Mass Measurement of the Top Quark Mass - arxiv: [hep-ex] Single lepton (l + jets) or two leptons (dilepton) channels Events with one or two isolated charged leptons with relatively high p T and ET miss accounting for neutrinos. Also at least two b-jets are required Template method Monte Carlo (MC) simulated template distributions are re-constructed for a chosen observable sensitive to m top l + Jets Channel (Selected Events) m reco top Variable / mtop Parameter jamkoons@gmail.com Top Quark Properties 19 / 28

25 Recent Measurements of Top Quark Properties Top Quark Mass Measurement of the Top Quark Mass - arxiv: [hep-ex] For the l + jets channel, the additional parameters JSF and bjsf are also fitted to data through the observables mw reco and Rbq reco respectively, sensitive to them Signal and background shapes are parametrised and a binned likelihood distribution is built to extract the parameters A tridimensional fit is performed for the l + jets channel (m top, JSF, bjsf) A one dimentional fit is performed for the dilepton channel (m top) Fit with Data / l + Jets Channel Fit with Data / Dilepton Channel jamkoons@gmail.com Top Quark Properties 20 / 28

26 Recent Measurements of Top Quark Properties Top Quark Mass Measurement of the Top Quark Mass - arxiv: [hep-ex] The measured values for parameters for l + jets and dilepton analyses are: m l+jets top = ± 0.75 (stat) ± 1.02 (syst) GeV, JSF = ± (stat) ± (syst), bjsf = ± (stat) ± (syst), mtop dil = ± 0.54 (stat) ± 1.30 (syst) GeV Overall combination: ATLAS best combination from a single analysis = ± 0.48 (stat) ± 0.78 (syst) GeV = ± 0.91 GeV m comb top JSF / mtop l+jets 2D Likelihood Scan mtop dilepton 1D Likelihood Scan jamkoons@gmail.com Top Quark Properties 21 / 28

27 Recent Measurements of Top Quark Properties CONF , L int -1 = fb =35 pb Top Quark Mass Evolution of Top Quark Mass Measurements Tevatron + LHC (world) combination arxiv: [hep-ex] m top = ± 0.27 (stat) ± 0.71 (syst) GeV Recent Tevatron overall combination arxiv: [hep-ex] m top = ± 0.37 (stat) ± 0.52 (syst) GeV CMS overall combination arxiv: [hep-ex] m top = ± 0.13 (stat) ± 0.47 (syst) GeV Evolution of Uncertainty (Figure by Chris Quigg) Level of precision reached 0.3 % Mar/2014 Jul/2015 Sep/2015 Recent m top Measurements and Combinations ATLAS Preliminary m top summary - Mar. 2015, L = 35 pb fb int CONF l+jets* ± 6.3 ( 4.0 ± 4.9 ) L int = 35 pb Eur. Phys. J. C72 (2012) 2046 l+jets ± 2.4 ( 0.6 ± 0.4 ± 2.3 ) L int = 1.04 fb CONF all jets* ± 4.3 ( 2.1 ± 3.8 ) L int = 2.05 fb arxiv: all jets ± 1.8 ( 1.4 ± 1.2 ) L int = 4.6 fb CONF single top* ± 2.1 ( 0.7 ± 2.0 ) L int =20.3 fb l+jets arxiv: ± 1.27 ( 0.23 ± 0.25 ± 0.67 ± 1.02 ) L int = 4.7 fb dilepton arxiv: ± 1.41 ( 0.54 ± 1.30 ) L int = 4.7 fb m top ± tot. (stat. ± JSF ± bjsf ± syst.) σ (tt) l+jets σ (tt) dilepton L int σ (tt+1-jet)* CONF L int =4.6 fb Eur. Phys. J. C74 (2014) ± ± ± 2.1 ATLAS Comb. Mar (arxiv: ) ± 0.91 World Comb. Mar (arxiv: ) ± 0.76 Tevatron Comb. Jul (arxiv: ) ± 0.64 World Comb. ± 1 σ stat. uncertainty stat. JSF bjsf uncertainty total uncertainty *Preliminary, Input to ATLAS comb m top [GeV] jamkoons@gmail.com Top Quark Properties 22 / 28

28 Recent Measurements of Top Quark Properties Top Quark Width Measurement of the top quark width in t t decays jamkoons@gmail.com Top Quark Properties / 28

29 Recent Measurements of Top Quark Properties Top Quark Width Measurement of the Top Quark Width - arxiv: [hep-ex] The CDF collaboration reported the first result using a direct approach, using the same analysis technique as the ATLAS collaboration Γ SM top 1.33 GeV It took 10 years for CDF to produce optimized result 1.10 < Γ top < 4.05 GeV at 68 % confidence level and Γ top < 6.38 GeV at 95 % confidence level The CMS collaboration following the D collaboration indirect approach has measured Γ top, arxiv: [hep-ex] Γ top = 1.36 ± 0.02 (stat) (syst) CDF Direct Measurement CMS Indirect Measurement jamkoons@gmail.com Top Quark Properties 23 / 28

30 Recent Measurements of Top Quark Properties Top Quark Width Measurement of the Top Quark Width Γ top(m top) = G F m 3 top 8π 2 ( 1 m2 W m 2 top ) 2 ( 1 2m2 W m 2 top ) [ 1 2αs 3π ( 2π 2 5 )] 3 2 SM Dependence (1) k f (m) = (m 2 mtop 2 )2 + mtop 2, k = 2 2mtopΓγ, γ = Γ2 π m top 2 + γ m 2 top (m2 top + Γ2 ) Mass Resonance (2) Standard Model Γ top(m top) dependence Templates at Truth Level Normalized Entries (Log Scale) µ + jets channel Default MC Rel Breit-Wigner Γ t Fitted Breit-Wigner Γ t Rel Breit-Wigner Γ t = 0.1 GeV = 1.33 GeV = 10 GeV Ldt = 20.3 fb s = 8 TeV -1 Fit mean = ± 0.5 GeV Fit width = ± GeV truth m top [GeV] jamkoons@gmail.com Top Quark Properties 24 / 28

31 Recent Measurements of Top Quark Properties Top Quark Width Measurement of the Top Quark Width with ATLAS - To be published ATLAS has performed its first measurement of Γ top using a direct approach in the l + jets channel The m t observable is reconstruted with χ 2 and KL-Fitter techniques. A template method is used to measure the parameter Γ top from data Selected Events Observable (m t ) Distribution Events ATLAS work in progress µ + jets channel Ldt = 20 fb s = 8 TeV -1 Data Background 0.4 GeV 1.3 GeV 3.0 GeV 5.0 GeV 7.0 GeV 10.0 GeV 15.0 GeV MC / Data m t [GeV] jamkoons@gmail.com Top Quark Properties 25 / 28

32 Recent Measurements of Top Quark Properties Top Quark Width Measurement of the Top Quark Width with ATLAS - To be published A binned likelihood profile is build to measure Γ top from data. Pseudo-experiments are performed to evaluate statistical and systematic uncertainties From the obtained uncertainties confidence belt and the measured Γ top, the upper limits for Γ top are: Γ top < 4.60 GeV at 68 % confidence level and Γ top < 7.16 GeV at 95 % confidence level Likelihood Profile with Data Confidence Intervals and Measurement -2lnL + κ 6 5 µ + jets channel Ldt = 20 fb s = 8 TeV -1 [GeV] input Γ top s = 8 TeV, 20.3 fb µ + jets Γ top [GeV] % C.L. stat only 95 % C.L. stat only 68 % C.L. stat + syst 95 % C.L. stat + syst Measured Γ t meas Γ top [GeV] jamkoons@gmail.com Top Quark Properties 26 / 28

33 Progress with LHC Run-II Precision Measurements Run-II will be era for precision measurements in top and higgs physics ATLAS went through important upgrades during LS1, before the start of Run-II in all areas: detector, online, offline and computing For proton-proton collisions at s = 13 TeV the t t events cross-section is expected to increase by a factor 3.3 with respect production at s = 8 TeV Number of events used for analyses will be substantially larger than in Run-I Sources of systematic uncertainties are well understood so much more precise measurements will be achieved during Run-II ] -1 Total Integrated Luminosity [fb ATLAS Online Luminosity s = 13 TeV LHC Delivered ATLAS Recorded -1 Total Delivered: 3.12 fb -1 Total Recorded: 2.86 fb 0 26/05 25/06 26/07 26/08 26/09 27/10 Day in 2015 jamkoons@gmail.com Top Quark Properties 27 / 28

34 Outlook Outlook The ATLAS collaboration has experienced a productive period during LHC Run-I Focusing on the understanding of sources of systematic uncertainties (main limitation for most measurements) Several top properties have been measured, obtaining comparable results with the measuremets from Tevatron experiments Higher precision for all measurements is expected during Run-II The collaboration is already fully engaged with analyses with data from collisions at s = 13 TeV (highest collider energies ever reached) Data collection is ongoing, MC calibration and pileup studies are in progress and some preliminary measurements have already been performed During Run-II searches for new physics will be attempted exhaustively See additional slides with more plots & complementary information jamkoons@gmail.com Top Quark Properties 28 / 28

35 Backup Backup Top Quark Properties / 28

36 Backup The LHC Basic Features CERN s Large Hadron Collider (LHC) The LHC extends to both sides of the border between France and Switzerland jamkoons@gmail.com Top Quark Properties / 28

37 Backup The LHC Basic Features Acceleration complex at CERN Proton bunches are produced, split and accelerated sequentially through different accelerators before injection into the LHC Top Quark Properties / 28

38 Backup The LHC Experiments Main Experiments Incorporated to the LHC CMS Is a multi-purpose detector with similar aims as ATLAS, with a large superconducting solenoid that produces a magnetic field 4 T. The measurements from ATLAS and CMS can be combined in most cases ALICE Used to analyze particles from lead nucleus-nucleus, Pb-Pb, head-on collisions. These generate very dense matter states such as the quark gluon plasma LHCb It s main purpose is the identification of small asymmetries between matter and antimatter from interactions that involve B-meson particles, made up with a b-quark TOTEM These detectors attempt to measure the cross section of proton - proton interactions, the luminosity of the LHC and to perform difractive studies that are not accesible in other detectors LHCf Studies particles from proton - proton collisions produced at very small angles in order to calibrate large scale cosmic ray experiments jamkoons@gmail.com Top Quark Properties / 28

39 Backup The ATLAS Experiment The ATLAS Detector Top Quark Properties / 28

40 Backup The ATLAS Experiment Available Data Recorded by the ATLAS Detector Top Quark Properties / 28

41 Backup The ATLAS Experiment Available Data Recorded by the ATLAS Detector Top Quark Properties / 28

42 Backup Charge Asymmetry Measurement of Charge Asymmetry - arxiv: [hep-ex] Selection Requirements jamkoons@gmail.com Top Quark Properties / 28

43 Backup Charge Asymmetry Measurement of Charge Asymmetry - arxiv: [hep-ex] For differential measurements it is not possible to distinguish between the SM and Beyond the SM (BSM) models at this level of precision Differential measurements are performed as a function of the variables m t t, β z,t t and p T,t t y Distributions Measured A c jamkoons@gmail.com Top Quark Properties / 28

44 Backup Charge Asymmetry Measurement of Charge Asymmetry - arxiv: [hep-ex] A measurement of the t t production charge asymmetry in the l + jets channel from proton-proton collisions at centre-of-mass energy s = 8 TeV A likelihood fit is used to reconstruct the t t system Selected events Reconstructed t t invariant mass jamkoons@gmail.com Top Quark Properties / 28

45 Backup Charge Asymmetry Measurement of Charge Asymmetry - arxiv: [hep-ex] ATLAS and CMS measurements on A C are compared with the t t forward-backward asymmetry A FB measured by the Tevatron by CDF and D0 experiments Several BSM models predic a especific relationship between these two asymmetries, so far the measured values for both asymmetries by four different experiments agree with the SM predictions y Distributions Measured A c jamkoons@gmail.com Top Quark Properties / 28

46 Backup Color Flow Measurement of Color Flow in t t events - arxiv: [hep-ex] The distribution and orientation of energy inside jets is predicted to be an experimental handle on color connections between hard-scatter quarks and gluons initiating jets previous studies by D0 experiment Strength and direction of the strong force depends on the colour charge of the particles involved jamkoons@gmail.com Top Quark Properties / 28

47 Backup Top Quark Mass Measurement of the Top Quark Mass - arxiv: [hep-ex] Single lepton (l + jets) or two leptons (dilepton) channels Events with one or two isolated charged leptons with relatively high p T and ET miss accounting for neutrinos. Also at least two b-jets are required l + Jets Channel Dilepton Channel jamkoons@gmail.com Top Quark Properties / 28

48 Backup Top Quark Mass Measurement of the Top Quark Mass - arxiv: [hep-ex] Template method is used for all channels to extract m top Monte Carlo (MC) simulated template distributions are constructed for a chosen observable sensitive to m top The KL-Fitter algorithm is used to reconstruct the t t event topology for the l + jets channel from where the mtop reco observable is extracted For the dilepton channel the m top-sensitive mlb reco is obtained using event leptons and b-jets mtop reco Variable / mtop Parameter mreco lb Variable / m top Parameter jamkoons@gmail.com Top Quark Properties / 28

49 Backup Top Quark Mass Measurement of the Top Quark Mass - arxiv: [hep-ex] For the l + jets channel, the additional parameters JSF and bjsf are also fitted to data Modelling of the MC with data improves Additional fits reduce the size of the systematic uncertainty To measure these parameters, the observables mw reco constructed m reco W and R reco bq Variable / JSF Parameter Rreco bq sensitive to them are Variable / bjsf Parameter jamkoons@gmail.com Top Quark Properties / 28

50 Backup Top Quark Mass Measurement of the Top Quark Mass - arxiv: [hep-ex] For l + jets and dilepton channels events with 1 or more b-tagged jets from muon or electron sub-channels were combined statistical uncertainty is reduced Signal and background shapes are parametrised and then fitted to data. Parameters are extracted from the maximisation of a likelihood expression A tridimensional fit is performed for the l + jets channel (m top, JSF, bjsf) A one dimentional fit is performed for the dilepton channel (m top) Fit with Data / l + Jets Channel Fit with Data / Dilepton Channel jamkoons@gmail.com Top Quark Properties / 28

51 Backup Top Quark Mass Measurement of the Top Quark Mass - arxiv: [hep-ex] The measured values for parameters for l + jets and dilepton analyses are: m l+jets top = ± 0.75 (stat) ± 1.02 (syst) GeV, JSF = ± (stat) ± (syst), bjsf = ± (stat) ± (syst), m dil top = ± 0.54 (stat) ± 1.30 (syst) GeV Fit with Data / l + Jets Channel / m reco W Fit with Data / l + Jets Channel / R reco qb jamkoons@gmail.com Top Quark Properties / 28

52 Backup Top Quark Mass Measurement of the Top Quark Mass - arxiv: [hep-ex] The three dimensional l + jets analysis in general decreases sizes of uncertainties and makes the two channels (l + jets and dilepton) less correlated After the combination m top results from both channels, the final obtained result is: m comb top = ± 0.48 (stat) ± 0.78 (syst) GeV = ± 0.91 GeV JSF / mtop l+jets 2D Likelihood Scan mtop dilepton 1D Likelihood Scan jamkoons@gmail.com Top Quark Properties / 28

53 Backup Top Quark Mass Measurement of the Top Quark Mass - arxiv: [hep-ex] jamkoons@gmail.com Top Quark Properties / 28

54 Backup Top Quark Mass Measurement of the Top Quark Mass - arxiv: [hep-ex] jamkoons@gmail.com Top Quark Properties / 28

55 Backup Top Quark Width Measurement of the Top Quark Width - arxiv: [hep-ex] The CDF collaboration reported the first result using a direct approach, using the same analysis technique as the ATLAS collaboration It took 10 years for the CDF collaboration to produce their optimized result on top quark width Γ top The mt reco observable is reconstructed using a χ 2 technique, producing templates with different values Γ top (0, 10) GeV The CDF result can be summarized as 1.10 < Γ top < 4.05 GeV at 68 % confidence level and Γ top < 6.38 GeV at 95 % confidence level Reconstructed Γ top templates Confidence Intervals and Measurement jamkoons@gmail.com Top Quark Properties / 28

56 Backup Top Quark Width Indirect Measurement of the Top Quark Width - arxiv: [hep-ex] Γ top = B(t W + b) R = B(t W + q) σ t channel B(t W + b) Γ th(t W + b) σ theory t channel The CMS collaboration following the D collaboration indirect approach has measured Γ top The result from CMS is Γ top 1.36 ± 0.02 (stat) (syst) Single Top Channel Confidence Intervals and Measurement (3) (4) jamkoons@gmail.com Top Quark Properties / 28