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Searches for di-lepton and di-photon resonances at ATLAS 1OCPA7, Yanwen Liu/USTC Yanwen Liu University of Science and Technology of China (USTC) On behalf.

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Presentation on theme: "Searches for di-lepton and di-photon resonances at ATLAS 1OCPA7, Yanwen Liu/USTC Yanwen Liu University of Science and Technology of China (USTC) On behalf."— Presentation transcript:

1 Searches for di-lepton and di-photon resonances at ATLAS 1OCPA7, Yanwen Liu/USTC Yanwen Liu University of Science and Technology of China (USTC) On behalf of the ATLAS collaboration Aug 4, 2011. Kaohsiung

2 Outline LHC and ATLAS Searches with photon pairs – Higgs – Gravitons Searches with lepton pairs – Gravitons – Z’ – R-parity violating sneutrino Summary 2OCPA7, Yanwen Liu/USTCAug 4, 2011. Kaohsiung

3 Experiments at LHC Aug 4, 2011. Kaohsiung3 +LHCf, TOTEM OCPA7, Yanwen Liu/USTC

4 Inner detector (B=2 T) Si pixels and strips Transition Radiation Detector (e/  separation)  /p T ~ 0.05% p T (GeV)  0.1%; |  | < 2.5, B=2 T(central solenoid) Hadron Calorimeter Fe/scintillator (central), Cu/W-LAr (fwd)  /E ~ 50%/√E(GeV)  3% |  |<3 Muon spectrometer air-core toroids, MDT+RPC+TGC+CSC  /p T ~ 2-7 % |  | < 2.7, |  |<2.5 ( precision phys.) EM Calorimetry Pb-LAr  /E ~ 10%/√E(GeV)  1% |  |<3.2, |  | < 2.5 (fine granularity) Length: ~ 46 m Radius : ~ 12 m Weight : ~ 7000 tons Channels: ~ 10 8 L cable : ~ 3000 km Cost: 541M CHF Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC4

5 Data collection Aug 4, 2011. Kaohsiung5OCPA7, Yanwen Liu/USTC 7 TeV 2010: Exponential ramping up of luminosity data-taking efficiency ~95% Peak luminosity : 1.75x10 33 cm -2 s -1 2011: steadily delivering !

6 Search for Higgs in di-photons Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC6 arxiv: 1107.0975v1 http://cern.ch/gfitter Low mass Higgs is favored by the global electroweak fitting. γγ is one of the most promising channels at low mass.

7 Analysis overview Two photon candidates P T 1 >40 GeV, P T 2 >25 GeV, 1.52<|η|<2.37 and |η|<1.37 Background : γγ(~70%), γj +jj (~28%) and ee(~2%, relevant near Z pole) Events are divided into 5 non-overlapping categories for different signal/background and resolutions Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC7 No significant excess m H =120 GeV, expect ~18 events

8 The ATLAS picture on Higgs Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC8 Dominating systematic uncertainties for γγ channel: signal normalization: photon ID efficiency (11%) mass resolution : 14% in total.

9 Randall-Sundrum gravitons Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC9 A possible “explanation” to the hierarchy problem One extra dimension of finite size(r c ), φ : 0 -> π. “Warped” metric: K-K excitation of gravitons observable at hadron colliders Two model parameters: k/Mpl, m G PRL83(1999)3370

10 RS limits from 2010 data Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC10 2011 data analysis in progress. Mass > 920 (545) GeV for k/Mpl=0.1(0.02) Excluded at 95%CL

11 Search Di-lepton resonances Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC11 e+e-e+e- μ + μ - Two isolated electrons with E T >25 GeV. |η|<1.37 and 1.52<|η|<2.47 For 1500 GeV Z’, acceptance ~65% Two isolated muons with P T >25 GeV For 1500 GeV Z’, acceptance ~40% Background estimated using MC simulations. Normalized to data using 70 GeV { "@context": "http://schema.org", "@type": "ImageObject", "contentUrl": "http://images.slideplayer.com/13/3874056/slides/slide_11.jpg", "name": "Search Di-lepton resonances Aug 4, 2011.", "description": "KaohsiungOCPA7, Yanwen Liu/USTC11 e+e-e+e- μ + μ - Two isolated electrons with E T >25 GeV. |η|<1.37 and 1.52<|η|<2.47 For 1500 GeV Z’, acceptance ~65% Two isolated muons with P T >25 GeV For 1500 GeV Z’, acceptance ~40% Background estimated using MC simulations. Normalized to data using 70 GeV

12 Constraints on RS gravitons and Z’ Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC12 0.7 TeV for k/Mpl= 0.01 1.63 TeV for k/Mpl = 0.1 1.83 TeV SSM RS gravitons, spin=2 Two benchmark models Sequential Standard Model (SSM) E6 : SU(5)xU(1)xU(1) The two U(1) fields can mix

13 Search for e+μ resonances Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC13 Example models: Lepton-Flavor-Violating Z’ R-parity violating sneutrino. For 0.7 TeV Z’, σ(pp->Z’+X)*Br(Z’->eμ) < 10.7 fb λ 311 ’, λ 312 ≠ 0 All other couplings = 0

14 Summary No discoveries in 1fb -1. We will have much more data soon Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC14 One of the projections presented at EPS 2011. Not validated by LHC Machine Committee. Stay tuned! log scale!

15 THANKS! Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC15

16 BACK-UP Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC16 Some slides are borrowed from EPS 2011 talks

17 Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC17

18 ATLAS Higgs-> γγ categories Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC18

19 Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC19

20 CMS Higgs status Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC20

21 H   Low sensitivity, high resolution (1-2 GeV today but further improvements possible), tiny signal on a smoothly falling background; challenges: vertexing with PU, calibrations and transparency corrections for the crystals. CMS PAS-HIG-11-011CMS PAS-HIG-11-010 Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC21

22 CDF Higgs status Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC22

23 Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC23

24 Tevatron Higgs status Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC24

25 Tevatron Combination Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC25

26 High p T di-leptons Z’-Z’- 1940 GeV for the Sequential Standard Model Z′ SSM, 1620 GeV for Super-String inspired models, Z′ ψ. 1450-1780 GeV for RS Kaluza-Klein Gravitons for (k/M Pl ) 0.05- 0.1. Z’/G KK We study in detail the high mass tail of the Z. Since spectra are consistent with known SM processes we extract 95% CL limits. CMS-PAS-EXO-11-019. Z’e+e-Z’e+e- Z’  e + e - or    - Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC26

27 LHC 2011 schedule Aug 4, 2011. KaohsiungOCPA7, Yanwen Liu/USTC27


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