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, Kaohsiung

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, Kaohsiung

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

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, KaohsiungOCPA7, Yanwen Liu/USTC4

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

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

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, KaohsiungOCPA7, Yanwen Liu/USTC7 No significant excess m H =120 GeV, expect ~18 events

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

Randall-Sundrum gravitons Aug 4, 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

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

Search Di-lepton resonances Aug 4, 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<M<110 GeV (scaling factor differs from 1 by less than 1%)

Constraints on RS gravitons and Z’ Aug 4, KaohsiungOCPA7, Yanwen Liu/USTC TeV for k/Mpl= TeV for k/Mpl = 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

Search for e+μ resonances Aug 4, 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

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

THANKS! Aug 4, KaohsiungOCPA7, Yanwen Liu/USTC15

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

Aug 4, KaohsiungOCPA7, Yanwen Liu/USTC17

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

Aug 4, KaohsiungOCPA7, Yanwen Liu/USTC19

CMS Higgs status Aug 4, KaohsiungOCPA7, Yanwen Liu/USTC20

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 CMS PAS-HIG Aug 4, KaohsiungOCPA7, Yanwen Liu/USTC21

CDF Higgs status Aug 4, KaohsiungOCPA7, Yanwen Liu/USTC22

Aug 4, KaohsiungOCPA7, Yanwen Liu/USTC23

Tevatron Higgs status Aug 4, KaohsiungOCPA7, Yanwen Liu/USTC24

Tevatron Combination Aug 4, KaohsiungOCPA7, Yanwen Liu/USTC25

High p T di-leptons Z’-Z’ GeV for the Sequential Standard Model Z′ SSM, 1620 GeV for Super-String inspired models, Z′ ψ GeV for RS Kaluza-Klein Gravitons for (k/M Pl ) 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 Z’e+e-Z’e+e- Z’  e + e - or    - Aug 4, KaohsiungOCPA7, Yanwen Liu/USTC26

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