1 / 18

Measurement of and at

Measurement of and at. Reddy Pratap Gandrajula (University of Iowa) on behalf of CMS Analysis referance:BPH-12-011. Outline. Introduction CMS detector Analysis Strategy , and signals Results Summary and Conclusions. Introduction.

candie
Download Presentation

Measurement of and at

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Measurement of and at Reddy PratapGandrajula (University of Iowa) on behalf of CMS Analysis referance:BPH-12-011 APS April meeting 2014

  2. Outline • Introduction • CMS detector • Analysis Strategy • , and signals • Results • Summary and Conclusions APS April meeting 2014

  3. Introduction • LHC opened a new era for the flavor physics by copiously producing heavy flavors at 7 and 8 TeV. • One particle which deserves careful study is the meson, whose small cross-section has limited, so far, its experimental investigation. • A rich program of measurements is being carried out by LHCb at the complementary pseudorapidity region can be accessed by CMS APS April meeting 2014

  4. Introduction…. • CMS, with excellent muon identification system and tracker detectors, allows for and final state studies in a central region. • Measurements, driven by the in the final state provides basic information about the meson, which serve an introduction for further experimental investigation. g g APS April meeting 2014

  5. CMS & LHC • Good performance from LHC & CMS • Identifies and measures charged particles, Jets, etc. • In 2011 it collected 5.56 pp data. • Analysis is performed on 5.1 data. APS April meeting 2014

  6. Slice view of CMS Most important sub-detector elements for this analysis APS April meeting 2014

  7. Analysis Strategy • The analysis is driven by reconstruction: • Two oppositely – charged muons selected with the standard muon selection. • All triggers apply the following cuts: • , where is the pointing angle, in the transverse plane, between the dimuon momentum and the direction from the dimuon vertex to the beam spot. • >3, where is the transverse detachment between the dimuon vertex and the beamspot and is the corresponding uncertainty. • Dimuon vertex probability • Distance of closest approach between the two muons < 0.5 cm. APS April meeting 2014

  8. primary vertex primary vertex secondary vertex secondary vertex Analysis Strategy… • The cuts were tightened with increasing instant.Lumi. • , Dimuon vertex probability • Dimuon trigger matched • candidates: with 1 track, assuming that is a pion (kaon) • candidates: with 3 tracks, assuming that they are pions. APS April meeting 2014

  9. Analysis Strategy….. • The pion(kaon) candidates are required to have: • a track fit • Tracker hits>6, pixel hits 2, and • <6 (Inferred from MC). • for and • In analysis, is required for the highest track, while is required for the other two pions. • Vertex probability >0.1%; . • In case of multiple () candidates, the one with highest is retained. APS April meeting 2014

  10. Requirements for reconstructionand Cut optimization using and GeV/c; Vertex CL>6%; GeV/c; 1. • GeV/c; • Vertex CL>20%; • GeV/c; • 7GeV/c; • 9GeV/c; • where is taken from and derived from the momentum vector and the sum of the momentum vectors of the three pions APS April meeting 2014

  11. and mass fits • Signals modeled to a Gaussian fit, signal to a double Gaussian fit and background is modeled to 2nd order Chebyshev polynomial. • yield:9227; m:6.2660.006 • yield:17619; m:6.2670.003 • yield:90398357; m: 5.278470.00007 Bkg negligible Bkg negligible Bkg negligible APS April meeting 2014

  12. The ratio measurement • The ratio can be obtained through the relation: =, Where N is the number of signal events and is the overall analysis efficiency for the and reconstruction. • Pt dependent efficiency from MC - BCVEGPY for and PYTHIA for • Data are corrected event-by-event according to their and related MC efficiency. The efficiency corrected mass plots for and are shown here. APS April meeting 2014

  13. Substructure Study & Efficiency Parameterization • Data shows some hints of and resonances; but the yield (about 100) is too small to perform a detailed Dalitz analysis. • (Dalitz plot representation of five-body decay of a spinless particle) can be described in its center of mass by mass-combinations: , , , , , and ; the and subscripts refers to the lower and higher invariant mass combination where is involved. Where , , , , , , ; and are the free parameters in the 7th dimensional space. • The resulting efficiency function is used to weight the data event by event. The efficiency – corrected an unbinned maximum Likelihood fit on data is shown here. APS April meeting 2014

  14. Systematics The Systematic uncertainty The Systematic uncertainty Split data sample: No triggered periods(limit stat), pileup samples( and ). Fit variant: No variant w.r.t. signal shape(limit stat)and for bkg by a different order Chebyshevpolynomial( from 1st to 3rd ). MC finite size: MC reweighted evaluated through pseudo- experiment studies. Efficiency binning: Various bin values are tested for . Tracking efficiency: efficiency tracking uncertainty for each pion track of 3.9%. • Split data sample: three triggered periods, pileup samples( and ). • Fit variant: Default signal fit a single Gaussian, for syst. Study fit signal to a double Gaussian with widths fixed to MC values, and for bkg by a different order Chebyshev polynomial or exp. function. • MC finite size: MC reweighted and evaluated through pseudo- experiment studies. • Efficiency binning: Various bin values are tested for both and Big. Syst Big. Syst APS April meeting 2014

  15. Results:In a rapidity region complementary to LHCb • = • =2.43 +0.05 -0.03 +0.46 -0.44 APS April meeting 2014

  16. Summary and conclusions • The analysis of and is presented • CMS 7 TeV data permitted the measurement of the ratio:in a region complementary to that investigated by LHCb collaboration. • The analysis of also permitted the determination of the ratio: • Our results are in agreement with LHCb ones. APS April meeting 2014

  17. Questions ? APS April meeting 2014

  18. CMS standard soft Muon selection • Muon track should have at least 1 pixel hit and at least 5 silicon hits. • the normalized c2 of muon track < 1.8. • < 3.0 cm. • < 30.0 cm. • Tracker track matched with at least one muon segment (in any station) in both X and Y coordinates and arbitrated. • Triggers and Data Set: • Data Set: /MuOnia/Run2011A-08Nov2011-v1/AOD, /MuOnia/Run2011B-19Nov2011-v1/AOD • Unprescaled displaced vertex dimuon triggers are considered • HLT paths and Luminosity for the signal samples: APS April meeting 2014

More Related