Top mass & properties. LHCP, June 2018, Bologna. M. Vos, IFIC (UVEG/CSIC) Valencia, Spain, on behalf of the ATLAS and CMS collaborations

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1 Top mass & properties LHCP, June 2018, Bologna M. Vos, IFIC (UVEG/CSIC) Valencia, Spain, on behalf of the ATLAS and CMS collaborations

2 Top properties When the father heard that his son would give a talk about top properties, he said: son, I always knew you d eventually grow up and get a serious job in real estate

3 One goal: two approaches Probing BSM out to 4-5 TeV Leaving no stone unturned Facini, Kogler, Juste, Thursday Direct BSM searches VS. Precision physics at the LHC a closure test of the SM This talk: focus on subtle deviations SM mass & width (Nason, Naseri, Knue) charge & spin asymmetry (Leone, Knue) global EFT fit of the top sector (Maltoni) See also: single top (Brock), rare processes (Zevi) 3

4 Top properties - motivation M. Baak et al., arxiv: Tev.+LHC top mass combination MeV theory uncertainty Electroweak fit yields indirect mw = MeV Error budget dominated by mt mt: 5 MeV mz: 2.5 MeV mh: 1 MeV s: 2 MeV Top mass may drive the Higgs potential at high scale negative (But universe not likely to decay any time soon) Buttazzo et al arxiv: v4 4

5 The top quark mass The only quark whose mass can be determined directly Reconstructed top quark mass distribution at the Tevatron 5

6 Top quark mass - future Projection of exp. uncertainties HL-LHC, hep-ph/ : uncertainty (dominated by systematics) of 1 GeV [ ] more data offer no obvious improvement. Snowmass, arxiv: : a top mass extraction with uncertainty as low as MeV CMS-FTR PAS: 200 MeV [under] optimistic but not unrealistic assumptions. CMS-DP : Conventional methods [...] are expected to yield an ultimate relative precision below 0.1%. We re definitely more ambitious now than before the start of the LHC Projection of theory uncertainties FCC SM report, arxiv: : We avoid here a discussion of the determination of the top mass at 100 TeV: any progress relative to what will be known at the end of the LHC will depend on theoretical progress that is hard to anticipate. 6

7 Top mass interpretation This is QCD, the top quark has colour charge, mtpole - mt(mt) ~ O(10) GeV The observable and SM parameter are related by theory, fixing the scheme Yet, our papers present a measurement without stating the interpretation Good theory work, but no consensus on interpretation of most precise measurements Nason, , Corcella et al., , Butenschoen et al. PRL Progress towards a 0.1% quark mass measurement requires further theory work - interpretation, non-perturbative uncertainties, modelling uncertainties Talk by Nason in parallel session 7

8 See: Javier Fernandez talk Supporting measurements ATLAS 13 TeV, 36 fb1-1 arxiv: Colour flow is poorly modelled CMS 13 TeV, 36 fb-1 CMS-PAS-TOP Charged particle multiplicity due to UE is poorly modeled Variation among usual generators cover difference with data Opportunity to improve Monte Carlo generators 8

9 Top quark mass: direct LHC + Tevatron 2014: mt = ± 0.7 GeV arxiv: D0 combination (2017) mt = ± 0.8 GeV arxiv: CDF combination (2014) mt = ± 0.9 GeV ATLAS combination (2017) mt = ± 0.5 GeV CMS combination (2015) mt = ± 0.5 GeV 8 TeV, ATLAS l+jets, ATLAS-CONF TeV, ATLAS all hadronic, JHEP09 (2017) 13 TeV, CMS l+jets, arxiv: (36 fb-1, 600 MeV) 9

10 ATLAS 8 TeV, all-hadronic Fit to R3/2 = mjjj/mjj mt = GeV JHEP 09 (2017)

11 ATLAS 8 TeV 8 TeV, ATLAS l+jets, ATLAS-CONF D fit of mt, JES, bjes: mt = GeV 11

12 ATLAS di-lepton, 8 TeV ATLAS partial 8 TeV combination: 910 MeV (l+jets, ATLAS-CONF ) 850 MeV (di-lepton, PLB761 (2016) 350) Combination: 500 MeV!!! 12

13 CMS direct top mass at 13 TeV Raw W and top mass peaks 13

14 CMS direct top mass at 13 TeV W and top mass peaks after the fit 14

15 CMS direct mass at 13 TeV JSF free JSF =1 JSF prior Tremendous work in both collaborations to gain control over the jet response Still, a simultaneous fit of mass and JES is crucial for this precision 15

16 CMS direct mass at 13 TeV JSF free JSF =1 JSF prior Tremendous work in both collaborations to gain control over the jet response Still, a simultaneous fit of mass and JES is crucial for this precision 16

17 CMS direct mass at 13 TeV JSF free JSF =1 JSF prior Tremendous work in both collaborations to gain control over the jet response Still, a simultaneous fit of mass and JES is crucial for this precision 17

18 CMS direct top mass at 13 TeV Interesting dependence of mt on kinematics, also present in some MC generators Stat./stat.+syst 36 fb-1 at 13 TeV (lepton+jets) ± 0.08 (stat.) ± 0.62 (syst.) cf. 20 fb-1 at 8 TeV (lepton+jets) ± 0.16 (stat) ± 0.48 (syst) GeV Compatible results with new data and new MC: POWHEG v2 + PYTHIA 8, CUETP8M2T4 tune. Systematic uncertainty somewhat increased wrt 8 TeV (color reconnection) arxiv:

19 Alternative methods: pole mass The top quark pole mass is extracted from a (differential) cross section measurement with sufficient mass sensitivity Control over mass scheme, provided unfolding is independent of MC mass Inclusive cross section Precise measurements in e final state State-of-the-art NNLO+NNLL theory 19

20 Alternative methods: pole mass The top quark pole mass is extracted from a (differential) cross section measurement with sufficient mass sensitivity Control over mass scheme, provided unfolding is independent of MC mass Differential cross section Enhanced sensitivity + shape analysis Theory still NLO, but can be upgraded to NNLO soon in some analyses D0 pole mass (see talk Leone) mtt, pt distributions: mt = ± 2.5 GeV! FERMILAB-CONF ATLAS pole mass at 8 TeV di-lepton differential distribution EPJC77 (2017) 804 Running mass interpretation: Fuster et al., arxiv:

21 pole mass, ATLAS di-lepton differential Cross section measurement in e + jets final state, ATLAS 8 TeV, EPJC77 (2017) 804 Fit differential x-sec in 8 (di-)lepton observables with MCFM to extract PDF + top mass 21

22 pole mass, ATLAS di-lepton differential Avoid over-constraining the theory uncertainty by considering several scenarios with fixed/dynamical scales theory unc. to improve with NNLO Gao & Papanastasiou, PRD96 Mtpole = ± 0.9 (stat.) ± 0.8 (exp.) ± 1.2 GeV (theo.) = ± 1.6 GeV c.f. CMS-DP : 1.2 GeV precision on mtpole after 3 ab-1 22

23 Top mass - alternative methods Top mass measurement is a rich R&D area a testbed for BSM mass measurements, a place to understand generators, and an incubator to develop the methods of the future: ultimate precision with 3 ab-1 complementary systematics Several methods have been devised that avoid jets B-hadron lifetime remove JES as dominant exp. systematic offer cleaner view on interpretation issue Methods that run on different toplogies single top, CMS, EPJC77 (2017) 354 boosted top, CMS, EPJC77 (2017)

24 CP violation in top sector If you were worried that top and anti-top quarks might have a different mass they don t: m = ± 0.19 (stat.) ± 0.09!! (syst.) GeV CMS 8 TeV, PLB770 (2017) 50 Search for CP violation in tt events in T-odd, triple-product correlation observables Compatible with SM within 1% CMS 8 TeV, JHEP03 (2017) 101 CP asymmetries in b-hadron decays in tt ATLAS 8 TeV, JHEP02 (2017)

25 Top quark width The top quark has a width of ~1.3 GeV; this value is precisely predicted in the SM 1% scale uncertainty at NNLO, 6% including parametric uncertainty Possibly enhanced by BSM decays Indirect determination from Rb = BR(t Wb) BR (t Wq ) and t-channel single-top cross section D0 t = GeV CMS t = 1.36 ± 0.02 (stat.) GeV PRD85 (2012) PLB736 (2014) 33 Direct measurements from a (partial) kinematic reconstruction of the top decay Challenges: - exp: JES/JER and modelling - exp: mass dependence - theo: inclusion NLO decay + off-shell effects 25

26 Top quark width direct measurement Fit to mlb and Rmin(j,b) Width is extracted assuming mt = GeV ATLAS t = 1.76 ± 0.33 (stat.) GeV EPJC78 (2018) 2, 129 CMS 0.6 < t < 2.5 GeV at 95% CL TOP-PAS CDF t < 6.38 GeV at 95% CL PRL111 (2013)

27 Charge asymmetry Asymmetry in top quark pair production at NLO QCD Rodrigo, Kuhn, PRL 81 (1998), PRD 59 (1999) 27

28 Charge asymmetry Legacy from the Tevatron new physics? CDF, D0 combination forward-backward asymmetry in pp tt + X, PRL 120 (2018) no. 4 Some tension remains, most of the excitement gone See talk by Leone 28

29 Charge asymmetry The answer from LHC run I... Inclusive AC [%] LHC top WG combination of inclusive 7 and 8 TeV results arxiv: TeV 8 TeV ATLAS 0.6 ± ± 0.5 CMS 0.4 ± ± ± 0.7 (stat) ± 0.6 (syst) ± 0.23 (stat) ± 0.25 (syst) ± combination Standard Model NLO+NLO EW Bernreuther & Si, arxiv: NNLO+NLO EW Czakon et al., arxiv: Massacre in model zoo: many of the explanations of Tevatron excess ruled out 29

30 Charge asymmetry 8 TeV combination Experimental uncertainties: Jet Energy Scale Multi-jet background Radiation modelling Precision theory at the LHC: 10 times more precise than the measurement 30

31 Differential measurements AC vs. mtt PLB756 (2016) High mass yields: enhanced quark-initiated fraction enhanced BSM sensitivity Perello et al., arxiv: Englert et al. arxiv: Cerrito et al., arxiv: arxiv: Future directions to boost AC dedicated techniques c.f. ATLAS 8 TeV Forward? At LHCb? see arxiv: Lucchesi Associated tt +, see arxiv:

32 Top properties at 13 TeV NEW: CMS TOP ( differential cross-sections on 2016 data (absolute & normalized, parton & particle) nearly events in ee,, e final states with 81% purity pt, y, for t, t and tt + mtt, y(t,t), (t,t), y(l+,l-), (l+,l-),... Discrepancy between data and MC for pt spectrum remains Systematic uncertainty + explicit check that corrected results are unbiased See: Javier Fernandez 32

33 Top properties at 13 TeV NEW: CMS TOP differential cross-sections on 2016 data (absolute & normalized, parton & particle) nearly events in ee,, e final states with 81% purity pt, y, for t, t and tt + mtt, y(t,t), (t,t), y(l+,l-), (l+,l-),... Fixed-order calculations do better, but do not agree for pt Good agreement for rapidity and absolute rapidity difference 33

34 Charge asymmetry at 13 TeV Bernreuther et al., arxiv: Parton and particle level are roughly equally precise Lepton asymmetry is measured much more precisely 1% uncertainty, larger than 8 TeV measurement in lepton+jets All compatible with SM and 0 34

35 Chromo-magnetic dipole moment Normalized fiducial measurements for leptons are extremely precise CMDM affects total rate and lepton angle distributions Buarque Franzosi & Zhang, EFT for CMDM at NLO in PRD 91 (2015) % Confidence Intervals on CMDM < CtG/ 2 < 0.41 This measurement < CtG/ 2 < 0.43 CMS 8 TeV diff. x-sec < CtG/ 2 < 0.30 CMS 8 TeV incl. x-sec < CtG/ 2 < 0.73 Tevatron incl. x-sec Roadmap towards a truly global EFT fit in the top sector F. Maltoni 35

36 Summary Precision top property measurements are very demanding: experimental response, esp. jet response with pile-up Monte Carlo colour flow and UE measurements Monte Carlo NLO decay, off-shell Theory interpretation top mass Precision top properties program in full swing Legacy Tevatron AFB combination + new mt measurements First direct top mass measurements at 13 TeV (0.3% precision) Pole mass measurement reaches 1.6 GeV precision (0.9% precision) Direct width determination with sub-gev precision Stringent limits on CP-violation in top sector Legacy combination of run I charge asymmetry measurement + first 13 TeV result 36

37 Summary Precision top property measurements are very demanding: experimental response, esp. jet response with pile-up Monte Carlo colour flow and UE measurements Monte Carlo NLO decay, off-shell Theory interpretation top mass Precision top properties program at the LHC in full swing Legacy Tevatron AFB combination + new mt measurements First direct top mass measurements at 13 TeV (0.3% precision) Pole mass measurement reaches 1.6 GeV precision (0.9% precision) Direct width determination with sub-gev precision Stringent limits on CP-violation in top sector Legacy combination of run I charge asymmetry measurement + first 13 TeV result So far, SM 10 BSM 0, but stay tuned... 37

38 Summary Precision top property measurements are very demanding: experimental response, esp. jet response with pile-up Monte Carlo colour flow and UE measurements Monte Carlo NLO decay, off-shell Theory interpretation top mass Precision top properties program is in full swing Legacy Tevatron AFB combination + new mt measurements First direct top mass measurements at 13 TeV (0.3% precision) Pole mass measurement reaches 1.6 GeV precision (0.9% precision) Direct width determination with sub-gev precision Stringent limits on CP-violation in top sector Legacy combination of run I charge asymmetry measurement first 13 TeV property results So far, SM 10 BSM 0, but stay tuned we only need one goal to win this match!! 38

39 Summary Precision top property measurements are very demanding: experimental response, esp. jet response with pile-up Monte Carlo colour flow and UE measurements Monte Carlo NLO decay, off-shell Theory interpretation top mass Top properties at the LHC in full swing First direct top mass measurements at 13 TeV (0.3% precision) Pole mass measurement reaches 1.6 GeV precision (0.9% precision) Direct width determination with sub-gev precision Stringent limits on CP-violation in top sector Legacy combination of run I charge asymmetry measurement first 13 TeV property results So far, SM 10 BSM 0, but stay tuned we only need one goal to win this match!! 39