Quark Compositeness Search with γ Jet Final State

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Quark Compositeness Search with γ +Jet Final State at the LHC Satyaki Bhattacharya, Sushil S. Chauhan, Brajesh Choudhary, Debajyoti Choudhury Department of Physics & Astrophysics University of Delhi, India-CMS Meeting @ Delhi 28 th September 2007

Outline • Motivation for the Study • Earlier studies within the same model • Signal and Backgrounds • Future Plans 2

Motivation • Probes coupling of excited quark to its SM • • counterparts Physics at low luminosity (~100 pb-1 to 1 fb-1) Direct search for mass peak Limits can be set on parameter space much above the Tevatron reach Di-jet QCD background is reducible due to clean hard photon (with tight isolation cuts) 3

Earlier Work with Di-photon Final State ar. Xive: 0705. 3472 v 1[hep-ph] CMS IN 2007/039 Submitted to PRD (responding to referees comments) 4

Poster Presented at Lepton Photon 2007, Daegu, Korea SELECTED AS BEST POSTER IN EXPERIMENTAL PARTICLE PHYICS CATEGORY CERTIFICATE & PRIZE AWARDED 5

Signal and Backgrounds Ø Feynman diagrams for the signal. Mass Peak No Peak, Excess over SM part Ø Feynman diagrams for the γ+jet background (Type-I). Ø Z(jj)+γ and W(jj)+γ Background (Type-II). 6

Matrix Element for qg γ+Jet via q* SM Piece By: Prof. Debajyoti Choudhury 7

Background and X-sections Cross Section (pb) for backgrounds in different PT-hat bin Type-1: SM γ+jet Background – Non-Reducible Pt – hat 50 -100 Ge. V 100 -200 Ge. V 200 -400 Ge. V 400 -600 Ge. V 600 -1000 Ge. V 1000 -1500 Ge. V >1500 Ge. V qg 4458 425. 3 33. 2 1. 517 2. 22 x 10 -1 1. 19 x 10 -2 7. 6 x 10 -4 qqbar 375. 4 47. 44 5. 01 3. 15 x 10 -1 5. 66 x 10 -2 3. 77 x 10 -3 2. 77 x 10 -4 gg 8. 01 x 10 -2 3. 08 x 10 -3 7. 02 x 10 -5 6. 33 x 10 -6 1. 75 x 10 -6 5. 81 x 10 -9 1. 528 Interested above 200 Ge. V onwards. 8

Background and X-Section Type-2: From Z(jj)+ & W(jj)+ - small & reducible but comparable to gg γ+jet) Pt –hat 50 -100 Ge. V 100 -200 Ge. V 200 -400 Ge. V 400 -600 Ge. V 600 -1000 Ge. V 1000 -1500 Ge. V >1500 Ge. V Z(jj)+γ 2. 80 6. 18 x 10 -1 8. 61 x 10 -2 6. 18 x 10 -3 1. 20 x 10 -3 8. 47 x 10 -5 6. 54 X 10 -6 W(jj)+γ 2. 54 4. 81 x 10 -1 6. 06 x 10 -2 4. 09 x 10 -3 7. 39 x 10 -4 4. 68 x 10 -5 2. 9 x 10 -6 Type-3: SM Jet-Jet background where one of the Jet(s) fakes a Photon – Largest Background – Reduce with isolation requirements 9

Photon and Jets • Algorithm to “reconstruct” the photon at the generator level (Reference - Marco Pieri et al. CMS IN 2005/018, and CMS IN 2007/039 – our earlier study) § Select a seed with P , e±T> 5 Ge. V § Search around the seed in 10 x 10 crystal geometry in φ and η directions § With Δφ=0. 09 and Δη=0. 09 § Add 4 -momentum vectors of found EM objects § Vector additions provides Photon Candidate § For Jet used Iterative Cone Algorithm with R=0. 5 and seed PT 1. 0 Ge. V (Inclusive jet i. e. neutrinos and muons are included in the jet definition) 10

Preliminary Distributions (I) Generation cuts: PT-hat ≥ 190 Ge. V on partons with no cut on η Signal is qg γ+jet via q* All plots are for Lint=10 pb-1 11

Preliminary Distributions (II) Selection Cuts: PTγ ≥ 200 Ge. V, PT jet ≥ 200 GV | ηγ | ≤ 2. 5 , |ηjet | ≤ 2. 5 12

Preliminary Distribution (III) 13

Preliminary Distribution (IV) 14

Preliminary Distribution (V) Invariant Mass distribution without any isolation cuts Backgrounds and signal separately 15

Preliminary Distribution (VI) Isolation variables: To decide track minimum PT to count them as track (final state, pi±, e±, p± & K± are considered as tracks ) 16

Preliminary Distribution (VII) With Isolation cut: Riso ≤ 0. 35, ET SUM < 5 Ge. V Study in progress to understand other isolation variables such as – number of tracks etc. and optimize various isolation cuts 17

Future Plans • Complete the generator level study for q* to • γ+jet final state with large statistics and set limits on Λ and Mq* for CMS setup (Submit as CMS IN) This study will be presented in the SUSY/BSM meeting on 28 th September at CERN • At present interfacing γγ and • γ+Jet final states via q* within CMSSW framework as an external routine. Will soon provide. cfg file for both channels to the production team. 18

Thank you!

Backup Slides 20

Available Literature For Quark & Lepton compositeness: • Dijet channel (Phys. Rev. D-03110, Robert Harris hepph/9609319) • Drell -Yan (S. Jain et. al. hep-ex/0005025 ) • Gamma+Jet final State: ATLAS collaboration (ATL –PHYS-99 -002). (No such study exists for CMS) • Two photon final state: Some phenomenological studies have been done without complete SM background e. g. , Thomas G. Rizzo PRD v 51, Num-3 (No such study exists for CMS) v Existing Limit at the LHC’s center of mass energy, with two photon final state is: ~Λ >2. 8 Te. V for contact interaction (depends on kinematical cuts and luminosity) 21

Compositeness scale: • Λ >> sqrt (s-hat) : Contact interaction • Λ << sqrt (s-hat) : Excited state • Λ ~ sqrt (s-hat) : Model Dependent 22

Present Limit on M* Limits from Tevatron: – – CDF: M* > 80 Ge. V (q* q ) CDF: M* > 150 Ge. V (q* q W ) CDF (All channels): M* >200 Ge. V D 0 : M*> 200 Ge. V • Simulation study: Mass reach up to 0. 94 Te. V at Tevatron ( 2 Te. V, 2 fb-1, q* q-qbar) • ATLAS Study: upto 6. 5 Te. V at LHC ( f=fs=1, q* q ) 23

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