LHC･アトラス実験におけるヒッグス粒子探索の最新結果について

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1 LHC アトラス実験におけるヒッグス粒子探索の最新結果について田中純一東大 ICEPP

2 SM Higgs ATLAS ATLAS Results H->WW->lnln H->ZZ->4l (plus CMS) H->gg (plus CMS) Combination (ATLAS and CMS) Summary Contents 2

3 2011 データ 3 月 13 日 10 月 30 日 LHC 加速器グループのおかげで予想をはるかに上回るデータを取ることができました Delivered L=5.61 fb -1 Recorded L=5.25 fb -1 Peak luminosity@atlas ~3.6 x cm -2 s -1 Data-taking efficiency = ~93.6% 検出器が動いていなかった割合 = a few permil to 3.5% データ解析に使える割合 ( Good-quality decided by each detector group and performance group) = 90-96% ( fb -1 ) 3

4 パイルアップバンチ間隔が当初の予定の倍 (50ns) かつルミノシティが当初の 3-4 倍近くのためパイルアップが非常に多い Z->mm Event with 20 reconstructed vertices 8 月末青それ以降赤データ量は半々 => 特に後半データはパイルアップの効果の理解が重要 4

5 SM プロセスの断面積測定 SM expectationと良い一致が見られる 5fb -1 での数 ~30M W->en and mn events ~3M Z->ee and mm events ~60k ttbar events (>10 x total CDF and D0 ) 測定にはまだ昨年のデータだけのものもあるデータ解析中 W/Z J/psi などは Calibrations, Corrections に非常に重要 5

6 ヒッグス粒子の生成と崩壊 (1) 現解析では Gluon fusion が主なチャンネル VBF はまだまだ NNLO+NNLL(QCD soft-gluon)+nlo EW NNLO+NLO EW NLO m H =125GeV: 15.3pb (ggf), 1.2pb(VBF), 0.6pb(WH), 0.3pb(ZH), 0.09pb(ttH) 6

7 ヒッグス粒子の生成と崩壊 (2) BR も含めて各モードのヒッグス粒子の生成 + 崩壊のまとめ 7

8 11 月までの結果 LEP+Tevatron LEP+Tevatron+ATLAS+CMS LEP m H >114.4GeV Tevatron 100<m H <109GeV 156<m H <177GeV ATLAS+CMS combination 141<m H <476GeV 124<m H <520GeV (expected) 残された領域 ( 軽い場合 ) は GeV ( 幅 27GeV) 8

9 12/13 のセミナーで見せた ATLAS の結果今日のトーク 9

10 H->WW->lnln L=2.05 fb -1 (~4.8 fb -1 は解析中 ) l = electron or muon 10

11 H->WW->lnln L=2.05 fb -1 Event Selection Single lepton trigger 2 isolated leptons 20GeV for elec, 15GeV for muon 25GeV for the leading lepton MET rel( )>40GeV(SF), 25(DF) Jets pt>25gev, eta <4.5 etc (see the next page) Z+jets E T miss is mix of fakes and real n s top E T miss from real n s [1] cannot reconstruct Higgs mass due to 2 neutrinos [2] Df(ll)->small -> low mass(ll) 11

12 m H =150GeV Before mll cut 12

13 mt 分布 after Df(ll) cut m H =130 GeV m H =150 GeV ( 左上と同じ 130GeV が重ねてある ) 13

14 H->WW->lnln の結果 Selection for m H =130GeV All ee em mm Observed data Expected BG 76(+-11) Expected signal (m H =130GeV) 19(+-4) Observed excluded = 145<m H <206GeV (expected: gev) Maximum deviation = 1.9s for m H ~130GeV 14

15 H->ZZ*->4l 15

16 H->ZZ->4l Event Selection (ATLAS) Single lepton trigger (>99.5%) 20-22GeV for elec, 18GeV for muon 4lep pt>20, 20, 7 and 7GeV Isolated and small impact param m Z -m 12 <15GeV m 34 <115GeV && Signal acceptance with eff is ~15% for m H =125GeV. (~48% for m H =200GeV) Performance of Low pt lepton gets important. CMS for comparison Dilepton trigger 4lep pt>20, 10 and 2 x (7GeV for elec or 5GeV for muon) 50 < m 12 < 120GeV 12 < m 34 < 120GeV 49%, 78%, 61% for 4e, 4m and 2e2m (m H =190GeV) 16

17 Electron Performance J/Y->ee, W->en and Z->ee Challenging->Low pt electrons Systematic uncertainty 6% pt~7gev <2% pt~50gev Pileup の影響 with Z->ee No Z-mass fit constraint ~82% in +-2s 17

18 Z->mm Muon rec eff > 95% (4<p T <100GeV) Muon Performance MC(perfect): 2.31 Data spring: 2.89 Data summer: 2.45 Pileup の影響 with Z->mm ~85% in +-2s No Z-mass fit constraint 18

19 3 events (<140GeV) 124.6(4m), 124.3(2e2m), 123.6(2m2e) Excess of GeV - Expected BG 16 events - Expected signal 11 events - Observed 22 events 19

20 4muon candidate with m 4l =124.6GeV p T =61.2, 33.1, 17.8, 11.6GeV m 12 =89.7GeV, m 34 =24.6GeV 20

21 4muon candidate with m 4l =124.3GeV p T =41.5, 26.5, 24.7, 18.3GeV m 12(ee) =76.8GeV, m 34(mm) =45.7GeV 21

22 BG check Z+jets, where jets fakes leptons. - 2 OS same-flavor with m Z +-15GeV - 2 additional SF leptons passing all cuts except for isolation and impact param. Z+mm Z+ee b -> m Jet -> e (p +- +p 0 ) b -> e 22

23 H->ZZ->4l Excluded three regions : , and GeV 23

24 H->ZZ->4l m H (GeV) Local (global) p 0 Local significance Expected % (~50%) 2.1s 1.4s % (~50%) 2.3s 3.2s % (~50%) 2.2s 1.5s LEE estimated over mass range: GeV 24

25 ATLAS vs CMS m H <180GeV Final 4e 4m 2e2m Obs Exp m H <160GeV 25

26 H->gg 26

27 H->gg Event selection 2g20 trigger E T >40GeV and 25GeV Isolated tight photon ETCone40<5GeV -> events in total (100<m gg <160GeV) Categorization => 9 Conversion status Eta region ptt=40gev 27

28 Background Processes = gg, gj and jj Fake photon jet->p 0 1/~10 4 (gluon>quark)(mc) Data η-strips jj ~ 500 μb γj ~ 200 nb ~ 30 pb H γγ ~ 40 fb 注意 : BG の成分をデータから見積もったが最終結果には使っていない 28

29 Mass mgg= 2E 1 E 2 (1-cosa) Mass Reconstruction Energy(E 1 and E 2 ) & Angle(a) between 2 photons Resolution は Pileup の影響をあまり受けない Conversionでまともなトラックがある場合はトラックを使うそれ以外は Calorimeterの層構造を利用する -> Primary vertexの選択にほぼ依存しない 29

30 Z->ee, J/Y->ee, W->en and MC Energy Calibration Energy scale at m Z ~ 0.5% Linearity < 1% Uniformity (constant term) ~1% for barrel and ~1.7% for endcap Electron -> photon by using MC MC has no constant term in this case 30

31 BG modeling Single exponential function with mass range of GeV Limits are obtained for GeV. Assign systematics for the choice of BG modeling 31

32 他の Functions もチェック 32

33 Systematic Uncertainties 33

34 H->gg の結果 m H =126GeV Local p-value = 0.27% -> 2.8s Global p-value = 7% -> 1.5s Expected = x SM ( ) Excluded = , GeV 34

35 35

ATLAS vs CMS Excluded = 114-115, 135-136GeV Expected = 1.6-2 x SM (110-140) Local p-value = 0.27%(2.

36 ATLAS vs CMS Excluded = , GeV Expected = x SM ( ) Local p-value = 0.27%(2.8s)@126GeV 27 Dec, 2011 KEK セミナー Excluded = GeV Expected = x SM ( ) Local p-value = 0.96%(2.3s)@123.5GeV 36

37 ATLAS and CMS Combination 37

38 ATLAS combination ATLAS 各チャンネル軽い部分は H->gg, H->WW->lnln, H->ZZ->4l 重い部分は H->ZZ->llnn ( 今回は更新しなかった ) 38

ATLAS combination Exclusion (95/99% CL Limit) Expected limit : 124.

39 ATLAS combination Exclusion (95/99% CL Limit) Expected limit : < m H < 520GeV Observed limit 95%: < m H < 115.5GeV, 131 <m H < 453GeV except for GeV 99%: 133 < m H < 230GeV, 260 < m H < 437GeV 39

40 ATLAS combination Exclusion (95% CL Limit) Observed limit (95%) < m H < 115.5GeV, 131 <m H < 453GeV except for GeV 40

41 ATLAS combination Excess at 126GeV Local p 0 -value: 0.019% -> 3.6s (expected ~2.4s) Global p 0 -value: 0.6% -> 2.5s with LEE over GeV Global p 0 -value: 1.4% -> 2.3s with LEE over GeV LEE=look elsewhere effect (resolution の良いチャンネルで重要 ->gg や 4l) 41

42 ATLAS combination Excess at 126GeV Local p 0 -value(126gev) - H->gg 2.8s - H->ZZ->4l 2.1s - H->WW->lnln 1.4s Local p 0 -value: 0.019% -> 3.6s (expected ~2.4s) Global p 0 -value: 0.6% -> 2.5s with LEE over GeV Global p 0 -value: 1.4% -> 2.3s with LEE over GeV 42

43 ATLAS combination SM Higgs に対する Best m 43

44 CMS combination 44

45 CMS combination Exclusion (95/99% CL Limit) Expected limit : 117 < m H < 543GeV Observed limit 95%: 127 < m H < 600GeV 99%: 128 < m H < 525GeV 45

46 CMS combination Excess at 119/124GeV 46

47 ATLAS 115.5<m H <131GeV CMS m H <127GeV ATLAS+CMS 115.5<m H <127GeV (Not combination but just AND ) 47

48 来年

Higgs x-sec 7->8TeV ~30% 向上 Additional 15-20 fb -1 with 8TeV in 2012 per one experiment -> Achieve 5s for

49 Higgs x-sec 7->8TeV ~30% 向上 Additional fb -1 with 8TeV in 2012 per one experiment -> Achieve 5s for GeV in the next year. (or exclude ~125GeV mass point.) (Achieve 5s down to 115GeV with ATLAS+CMS in the next year.) 49

Summary Higgs search at LHC in this year is very exciting! ATLAS still have several channels (tt/bb etc) to be updated. 115.

50 Summary Higgs search at LHC in this year is very exciting! ATLAS still have several channels (tt/bb etc) to be updated < m H < 127GeV Small excess around GeV is real? -> NO at the moment -> Still 2-3 sigma level with the look elsewhere effect. -> We need more data in the next year. 50

51 Backup 51

52 52

53 WW analysis, Control regions WW control regions - drop mt and Df(ll) cuts - m(ll)>80gev for m H <220GeV - m(ll)>180gev or 15<m(ll)<80GeV for m H >220GeV tt for 1-jet analysis control region - drop m T, m(ll) and Df(ll) cuts - b-jet tag 53

54 54

55 55

56 CMS H->gg 56

57 ATLAS vs CMS FWHM 4.35GeV => 3.5GeV (20% improvement!) 27 Dec, 2011 KEK セミナー 57

58 How to take into account LLE p global = p local + N exp(-(z 2 -Z 02 )/2) 58

59 CMS の図ですが Standard Model Still allowed low mass region ATLAS: 115.5<m H <131GeV CMS: m H <127GeV -> ATLAS+CMS 115.5<m H <127GeV (Not combination but just AND ) 59

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LHC-ATLAS 実験におけるタウレプトン対に崩壊するヒッグス粒子の探索中村浩二, 塙慶太 A, 田中純一, 増渕達也, 山村大樹東大素セ, 筑波大数理 A 2011 年 9 月 16 日日本物理学会 @ 弘前大 1 ヒッグス探索とタウチャンネル直接探索では mh