1. Study of pp  γ +N Jets Channel in CMS S. Bhattacharya, B.C. Choudhary, Pooja Gupta University of Delhi, India

2. Poona Gupta India-CMS Meeting BARC, Mumbai 2 OUTLINE Updates on Gamma + Jet work Gamma + N jets Work done at CERN Progress Future plans

3. Poona Gupta India-CMS Meeting BARC, Mumbai 3 Updates on Gamma + Jet work Presented as poster in XXVII Physics in Collisions held at Annecy, France from 26 th June 2007 to 29 th June 2007. Selected for Oral talk. A 15 minute presentation was given at the conference. The poster was also selected for a prize. This work has been accepted for poster presentation in Lepton- Photon 2007 to be held at Daegu, Korea.

4. Poona Gupta India-CMS Meeting BARC, Mumbai 4 Gamma + N jets Motivation In Continuation of previous work - Gamma + Jet using Pythia MC and OSCAR and ORCA for simulation & reconstruction – CMS NOTE 2007/004. Measurement of differential cross-section from the first data collection at the LHC. Event Generation Use Alpgen version 2.12 a Leading Order Generator for Event Generation. We are planning to generate Gamma + 1 jet, Gamma+ 2 jet, Gamma + 3 jet exclusive (i.e, Jet-parton matching) and Gamma + 4 jet inclusive samples. The proposal for Gamma + N jets events has been approved. Poona Gupta is responsible for providing the.cfg files and.grid2 files to the generator group.

5. Poona Gupta India-CMS Meeting BARC, Mumbai 5 Work done at CERN Dear colleagues, Poona was so kind to dig into the Alpgen production of photon+jets samples and after consulting with M. Mangano, Filip and me has put together the following proposal. If anyone else is interested in similar samples: Please have a look at the parameters and let us know wether or not they are fine for you. Filip, Poona and Klaus Here are the few points regarding the proposal. Please have a look. We are interested in generating Gamma + N jets sample where N =1, 2, 3, 4. 1. The Gamma + 1 jet, 2jet and 3 jet would be exclusive samples and gamma + 4 jet would be inclusive sample. 2. We are planning to modify the user routine in Phjetwork directory to do the Pt gamma binning as per the suggestions of M. Mangano. We are currently modifying the code and checking it. 3. The kinematical parameters for the input file would be : nph 1 njets 1 (1, 2, 3, 4 for different samples) ptjmin 20 (Default is 20 GeV) ptphmin 60 (Default is 20 GeV) etajmax 5.0 etaphmax 2.7 drjmin 0.7 drphjmin 0.7 We are interested in HLT photons hence the ptphmin is taken as 60 GeV. 4. The Pt gamma bins for each gamma + n jet sample would be : 60-120, 120-180, 180-240, 240-300, 300up Hence there would be 20 bins in total. 5. A minimum of 100 K events in each bin is required. That would sum upto 2-2.5 million events in total. Proposal for Event Generation

6. Poona Gupta India-CMS Meeting BARC, Mumbai 6 Work done at CERN Develop Skims which would be a part of QCDAnalysis Package: *** Discussion title: QCD Physics Hello Olga, Natalia and Filippo, you have all been added now as well as Poona Gupta and Sushil Chauhan. Concerning photon skims it would be a good idea to establish contact to Vladimir and Toyoka resp. Poona and Sushil if not done yet. Ciao, Klaus

7. Poona Gupta India-CMS Meeting BARC, Mumbai 7 Gamma + 1 Jet P T γ Min (Gev) P T jet min (GeV) P T γ bin (GeV) No. of weighted events Weighting efficiency Cross-sec (pb) No. of unweighted events Unweighti ng Efficiency Matching Efficiency 20 20 - 6042293200.4239.42E+0410167650.2400.680 602060 - 12049099480.4912.75E+0310787330.2200.583 12020120 - 18042480940.4252.16E+0210144950.2390.449 18020180 - 24046000440.4604.18E+0110311820.2240.393 24020240 - 30054677540.5471.20E+019795400.1790.328 30020300up54347980.5437.81E+0013321080.2450.276 Gamma + 1 Jet Exclusive N warm up : 8M Iterations : 6 N Events : 10M

8. Poona Gupta India-CMS Meeting BARC, Mumbai 8 Gamma + 2 Jets P T γ Min (GeV) P T jet min (GeV) P T γ Bin (GeV) No. of weighted events Weighting efficiency Cross-sec (pb) No. of unweighted events Unweighti ng Efficiency Matching Efficiency 20 20 - 60845680.0082.39E+04369130.4360.474 602060 - 1202658980.0272.77E+03319420.1200.400 12020120 - 1801138290.0113.04E+02343200.3020.323 18020180 - 2401582370.0166.76E+011036250.6550.282 24020240 - 3001870830.0192.11E+01892510.4770.227 30020300up1671770.0171.52E+01248950.1490.208 Gamma + 2 Jet Exclusive N warm up : 8M Iterations : 6 N Events : 10M

9. Poona Gupta India-CMS Meeting BARC, Mumbai 9 Gamma + 3 Jets P T γ Min (GeV) P T jet min (GeV) P T γ Bin (GeV) No. of weighted events Weighting efficiency Cross-sec (pb) No. of unweighted events Unweighti ng Efficiency Matching Efficiency 20 20 - 601548120.0151.00E+04154290.1000.293 602060 - 1202280440.0231.67E+03277470.1220.253 12020120 - 1802508870.0252.64E+02272340.1090.229 18020180 - 2401066770.0116.85E+01232250.2180.193 24020240 - 3001455550.0152.32E+01212590.1460.171 30020300up1193860.0121.85E+01239910.2010.149 Gamma + 3 Jet Exclusive N warm up : 10M Iterations : 6 N Events : 10M

10. Poona Gupta India-CMS Meeting BARC, Mumbai 10 Gamma + 4 Jets P T γ Min (GeV) P T jet min (GeV) P T γ Bin (GeV) No. of weighted events Weighting efficiency Cross-sec (pb) No. of unweighte d events Unweighti ng Efficiency Matching Efficiency 20 20 - 601024950.0071.70E+03118400.1161.000 602060 - 1201527860.0103.40E+02181170.1191.000 12020120 - 1801902790.0136.11E+01221610.1161.000 18020180 - 2401577230.0111.66E+01219210.1391.000 24020240 - 3001595250.0115.75E+00228030.1431.000 30020300up736680.0054.50E+00216870.2941.000 Gamma + 4 Jet Inclusive N warm up : 10M Iterations : 6 N Events : 15M

11. Poona Gupta India-CMS Meeting BARC, Mumbai 11 Matched Cross-sections Matched Cross-sections (pb) Pt Gamma Bin Gamma + 1 jet (Exclusive) Gamma + 2 jets (Exclusive) Gamma + 3jets (Exclusive) Gamma + 4 jets (Inclusive) 20 - 6064061.911354.22939.21700.9 60 - 1201603.01109.9423.4340.0 120 - 18096.798.260.361.1 180 - 24016.419.113.216.6 240 - 3003.94.84.05.7 300up2.23.22.84.5 This information is also available on the twiki page: https://twiki.cern.ch/twiki/bin/view/CMS/Alpgen-photon-nJets

12. Poona Gupta India-CMS Meeting BARC, Mumbai 12 Summary and Future Plans Develop expertise in CMSSW. The analysis script is being written. Prepare Skims and check them. Wait for the simulated data. Request for EM enriched multi-jet background events has been made. Waiting for the approval.

13. Backup Slides

14. Poona Gupta India-CMS Meeting BARC, Mumbai 14 Why Jet Parton Matching? Michelangelo Mangano, Lund University, Oct 7 2004

15. Poona Gupta India-CMS Meeting BARC, Mumbai 15 Why Jet Parton Matching? Michelangelo Mangano, Lund University, Oct 7 2004

16. Poona Gupta India-CMS Meeting BARC, Mumbai 16 Why Jet Parton Matching? Michelangelo Mangano, Lund University, Oct 7 2004