China Data Analysis Status Atlas Physics China Data Analysis Status 祝成光 山东大学物理学院 代表ATLAS实验中国组

The LHC Machine and Experiments LHC相比于现有的Tevetron加速器，质心能量提高了7倍，亮度提高了两个数量级。在这样一个全新的高能量范围提供高统计的样本，为许多物理研究提供了可能。 pp at 14 TeV, 1034cm-2s-1 High Energy  factor 7 increase w.r.t. present accelerator Tevatron High Luminosity Nevents/(s*T)  factor 100 increase

ATLAS Experiment and China Cluster Length ~ 46 m Diameter ~ 25 m Weight ~ 7000Ts Channel ~ 108 Cable ~ 3000km Inner detector (B=2 T) Si pixels and strips Transition Radiation Detector (e/ sep) s/pT ~ 0.05% pT(GeV)0.1%; |h| < 2.5, B=2 T(central solenoid) Hadron Calorimeter Fe/scintillator (central), Cu/W-LAr (fwd) s/E ~ 50%/√E(GeV)3%, up to ||<3 Muon spectrometer air-core toroids, MDT+RPC+TGC+CSC s/pT ~ 2-7 % |h|<2.5 (precise phys.) EM Calorimetry Pb-LAr s/E ~ 10%/√E(GeV)1% |h|<3.2, |h| < 2.5 (fine granularity) Inner Tracker: + vertex + b-tagging + pT & Q of track Calorimeter(EM+HD): + E of e/g + E of hadron jet + MET of n(c0) AATLAS的各个子探测器都具有良好的探测能力，特别对于那些大横动量的粒子和jet。Track的分辨率均几十个微米和量能器具有很好的粒度，对于精确测量提供了帮助 Muon(outmost tracker): + pT & Q m

Institution of High Energy Physics (IHEP): Higgs search and property study LCG Teir2 construction electron energy calibration and ID study Shandong University (SDU): W helicity measurement in top decay top spin correlation in pair production single top measurement Univ. of Science & Technology of China (USTC): WZ production and TGC anomalous coupling R-parity violation SUSY Nanjing University (NJU+SDU): single top measurement

Higgs production@ LHC q Higgs物理是ATLAS的重头戏，LHC上的SM higgs产生截面并不小，例如glon融合过程，在各种可能的higgs质量区域都是主要的产生方式。其他的产生方式，虽然截面小，但是由于伴随产生的其他特征明显的粒子的配合，能够容易的鉴别和压低本底，因此也是higgs研究的重要场所。 寻找higgs有许多优秀的衰变道，假设higgs能够找到，其性质的 研究将成为ATLAS物理的重要组成部分。

Higgs search@ ATLAS -- SM Higgs (114-190GeV) discovery @ 10 fb-1 -- easy and fast for mH >140 GeV with HWW* channel -- more strength on mH<140 GeV with Htt, Hgg 对于标准模型higgs的寻找，主要通过Hgammagamma 和tautau，以及HWW，对于更高的higgs质量，HZZ就成了最重要的寻找方式。

Photon/jet discrimination in Hgg (IHEP) -- Signal : gluon fusion production s(ggHgg)50fb in 95-130GeV mass region -- Background : irreducible photon pairs continuum sgg1pb/GeV reducible background s(g+j)103×sgg , s(j+j)106×sgg MVA Fisher: 8 variables_dijet 10 variables_dijet MVA HMatrix: -- MVA discriminator studies: IHEP研究了guon融合产生过程中的Hgammagamma过程，由于本底数量远远大于信号。其中对于gamma的鉴别是至关重要的问题，初步的研究表明某些方法能够明显的具有压低本底的优越性。IHEP同时研究了光子的分裂过程，首先发现光子在内部探测器中的分裂率远大于理论估计，是对ATLAS合作组的重要贡献。

Top Yukawa coupling in ttH(HWW*) (IHEP) -- Precise Yukawa couplings of heaviest fermion, in the intermediate ~160GeV mass gt -- Cross section measurement  coupling constant gt extraction CnL signal final state combination, I(mH) phase space integration 在ttH伴随产生中，精确测量yukawa coupling。SM给出不同的higgs质量，该过程的的产生+衰变截面，因此在某一特定的higgs质量区域，可以通过测量实际界面大小给出yukawacoupling的值。其中的HWW的衰变分支比通过和其他的Higgs衰变过程联合考虑来给出

Signal: same-signed 2L + 3L -- Topology and 2L/3L signal channel : Same-signed 2L/3L (from Higgs and top) >=4 high pT jets Missing ET for >=2n -- irreducible background : tt(1l/2l)+X(W,Z,jets) 由于末态有4各W，根据本底压制的需要，选择了其中的2L和3L过程进行测量。最重要的本底是tt+X过程，特别是某些jet中的轻子被误判为2L3L之一。虽然概率比较低但是tt的压倒性产生率使得本底很难得到控制。 lepton in heavy flavor e.g. bc+ln(W*) decay  signal same-signed “L” overwhelming QCD ISR and pileup  signal “jet” Isolation of L is crucial

Isolation in Calorimeter and tracker Lepton Isolated lepton Uniso. lepton Calo track Calorimeter Cone size 0.2 Inner detector Clusters around the lepton Tracks around the lepton Electron Muon Isolated sample of ttbar, uniso from b-jet samples 因此选取孤立轻子，并将误判率降到可以接受的程度是该研究的关键问题。选择孤立轻子的可以通过量能器和经迹探测器两种方式 Tracker Isolation: The maximum pt of extra tracks in ID around the lepton in a cone size of 0.2 should smaller than 2 GeV Calorimeter Isolation: The total energy deposited in the calorimeter around the lepton in a cone size of 0.2 should smaller than 10GeV

Theoretical uncertainties -- Uncertainty on Pythia ttH signal : PDF, Q2, ISR/FSR, fragmentation 理论误差

2L+3L combined prediction @ ATLAS 30fb-1 -- Accuracy on combined σttH×BRHWW -- Accuracy on coupling gt 这是全模拟数据给出的测量精度，其中主要的误差来源于本底数量的不确定性。 ATLAS CSC note的重要组成部分，editor是IHEP的张华侨 47.4% (@160GeV) 23.7% (@160GeV)

WH(WW*) measurement (IHEP) -- Complementary to heavy Higgs discovery: what if discovered via HZZ4l channel, while WH is absent? -- Measure cross-section to probe Higgs-gauge boson couplings -- Combined 2L+2j and 3L channel As property study, non-SM higgs? 如果通过HZZ找到Higgs，Wh的伴随产生过程就成重要的辅助验证过程，通过测量HW过程，来检验SM的预言 另外可以测量higgs和Wboson的耦合强度

Preliminary results 初步事例选择

Preliminary results -- Normalized to 30 fb-1 If 20% systematics WH2L Combined Significance 1.6 1.9 2.4 67% 64% 47% accepted in ATLAS CSC-NOTE WH coupling measurement in progress 测量精度，被ATLAS CSC note接受

Physics of top quark pair production Production cross section Heavy resonance decay W helicity Anomalous coupling CP violation Charge Width Mass Spin correlation Rare decays Branching ratios CKM :|Vtb| W: massless left-hand b  longitudinal or left-handed W heavy top with very short lifetime  100% weak decay before hadronilzation  t-tbar spin correlation will be preserved

W polarization and top-pair spin correlation (SDU) -- W helicity in top: σtt@LHC~850pb, Br(tWb)~100% governed by V-A in SM  spin=1/2 1 1/2 SM prediction(NLO): F0=0.695 FL=0.304 FR=0.001

-- top-pair spin correlation: where NLO SM prediction: 1) s1,s2 :: angle between t(tbar) and spin analysers 2) phi :: angle between spin analysers 3) 1, 2  spin analyzer qualities,for V-A: (l+) =1, (b)=-0.41….

Single lepton channel analysis -- high BR with moderate background -- in situ W and top mass(transverse) constraints *due to unknown discrepancy between fast and full simulation (730pb-1) (220pb-1) * NLO SM prediction:

Di-lepton channel analysis -- rare BR with rare background -- need to solve equations for missing ET of 2n

Single top measurement (NJU+SDU) t-channel (~247pb) W+t channel (~66pb) s-channel (~11pb) The only known way to directly measure CKM matrix element Vtb LHC t-channel 250pb 是直接测量Vtb的唯一方法。 期望能够区分各个channel，，比较困难

t-channel cut based analysis results Processes muon channel electron channel nEvt to L=fb-1 t-channel 3.83±0.15% 3.10±0.14% 1668 t-ch (τ)l 1.48±0.23% 0.36±0.11% s-channel 1.84±0.11% 1.14±0.08% 34 s-chan (τ)l 0.39±0.12% 0.39±0.12% W+t channel 0.85±0.07% 0.61±0.02% 136 W+t chan (τ)l 0.18±0.08% 0.20±0.08% ttl+jets 0.95±0.03% 0.69±0.02% 4173 tt(τ)l+j 0.35±0.04% 0.22±0.03% tte + e 1.83±0.12% ttμ+μ 3.07±0.16% ttμ+ e 2.10±0.09% ttμ+τ 3.18±0.11% tt e +τ 2.41±0.10% ttτ+τ 0.74±0.08% 初步选择结果 S/B = 1668/4343 = 38.4%, S/ √ S+B = 21.5

s-channel cut based analysis results Processes muon channel electron channel nEvt to L=fb-1 s-channel 2.47±0.12% 1.49±0.10% 46 s-ch (τ)l 0.71±0.16% 0.64±0.15% t-channel 0.22±0.04% 0.14±0.03% 84 t-chan (τ)l 0.04±0.04% 0.00±0.00% W+t channel 0.10±0.03% 0.08±0.03% 11 W+t chan (τ)l 0.00±0.00% 0.00±0.00% ttl+jets 0.09±0.01% 0.08±0.01% 646 tt(τ)l+j 0.04±0.01% 0.02±0.01% tte + e 0.34±0.05% ttμ+μ 0.48±0.06% ttμ+ e 0.33±0.04% ttμ+τ 0.69±0.05% tt e +τ 0.54±0.05% ttτ+τ 0.24±0.04% S/B = 46/741 = 6.2%, S/ √ S+B = 1.64

s-channel MVA analysis results@1fb-1 channel\classifiers BDT BDTD MLP LikelihoodD TMlpANN RuleFit sch-cut s-channel 50.3 46.0 36.0 40.1 40.0 35.0 46 t-channel 39.7 15.9 19.0 36.5 17.0 31.7 84 W+t channel 6.1 6.6 5.0 3.3 8.2 11 tt-->l+jets 88.9 64.7 70.2 114.7 45.2 104.5 223 tt-->di-lep 48.4 29.6 35.1 67.1 23.4 150 tt-->l+tau 75.7 74.1 141.2 60.1 97.5 273 all BKG 287.6 192.5 205.0 364.5 149.0 290.3 741 S/B 17.5% 23.9% 17.6% 11.0% 26.8% 12.1% 6.2% S/sqrt(S+B) 2.74 2.98 2.32 1.99 2.91 1.94 1.64 通过多参数分析方法提高SB

WZ cross-section and TGC anomalous measurement (USTC) SM NLO : Phys. Rev. D41, 2782(1990). Phys. Rev. D47, 940(1993). Phys. Rev. D60, 114037(1999). Phys. Rev. D60, 113006(1999) Unique measurement on WWZ TGC -- non-SM anomalous as with form factor as -- Enhancement on production + excess at W/Z high pT spectrum SM NLO xsection 3.7pb +/- 7% theoretical uncertainty Compared to WW channel, this associate production. WWZ TGC in WZ compared to WW where correlations between couplings of WWZ and WWg have to be applied 2) g_WWg=-e; g_WWZ=-e*cot(thW) 3) Anomalous are described as deviation from SM by these 3 parameters 4) Not only, but also, in pT spectrum high energy region 5) Very clean, but suffer from low Br  really need high luminosity to observe WZllln search channel : -- high pT isolated lepton + MET + di-lepton invariant mass around Z -- background Z(ll)+X and ZZ(4l) -- eee, eem, emm and mmm combined, Br~1.5%

WZ Observation @ 1fb-1 -- Simple straight cut results

R-parity violating sneutrio em resonance (USTC) Parity in SUSY can be partially violated in generic super-potential: -- Tri-linear on-spontaneous B- & L-number violation interactions  stable proton -- Bi-linear couplings  neutrino mass for oscillation -- Constraints from indirect low energy experiments l13k l31k LLE in tenn l312, l321 < 0.07 LQD in tpn l’311 < 0.12 With hypothesis: 1) degenerate M=100GeV 2) single coupling dominance It’s amazing to see theoretists as Weinburg proposed these RPV SUSY model, which could accommodate neutrino oscillation in later 1980s, before experimental confirmation With large statistic, low energy experiments provide some stringent constraints on RPV parameters, however, all of them are indirect searches on off-shell super-partner effects Reference: hep-ph/9906224; Phys. Rept. 420, 1(2005)

Expected result @ 1fb-1 -- Phenomenology in collider physics Y. B. Sun et al., Commun. Theor. Phys. 44, 107 (2005) L. L.Yang et al., Phys. Rev. D 72, 074026 (2005) S.M. Wang et al.,Phys. Rev. D 74, 057902 (2006) H. K.Dreiner et al., Phys. Rev. D 75, 035003 (2007) Y. Q. Chen et al., J. High Energy Phys. 05 (2007) 068 S.M. Wang et al., Chinese Phys. Lett. Vol.25, No.1(2008)58 -- Results of measured at Tevatron/D0  expected at ATLAS/LHC PRL 100,241803 ATLAS @ 1fb-1 的灵敏度比D0实验提高了10-20倍 10-20 folded improvement on RPV parameter sensitivity would be expected @ATLAS

ATLAS run LHC start tuning on 10/Sep First Collision expected soon with lower energy. Understand the detector and data is essential Follow up with free playing with real data.

Summary -- Physics analyses are taking shape, channels cover top, Higgs, EW and SUSY -- Stay tuned for the commissioning run: understanding detector, e.g. e/g efficiency, fake rate, energy scale and resolution, trigger performance etc is the 1st priority -- China LCG Tier2 construction is in good progress; need push university-level distributed Tier3 to be on line in time. -- Young graduates are heartly welcomed to join the team and enjoy yourself in the game for next 10-15 years.