1 / 23

Parton distribution function : W asymmetry

Parton distribution function : W asymmetry. W and Z production : Leading order process,. For measurable rapidity range, | Y |<2.5, x remains within 5 ×10 −4 < x < 5 ×10 −2.

chesmu
Télécharger la présentation

Parton distribution function : W asymmetry

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. Parton distribution function : W asymmetry W and Z production : Leading order process, For measurable rapidity range, |Y|<2.5, x remains within 5×10−4 < x < 5 ×10−2 At high Q2, gluon is dominant parton ⇨ sea quarks are generated by flavour blind g→qq splitting. Production rate is related to gluon distribution function With the assumption

  2. Some information from Generator (W) • Asymmetry is nearly flat over pt • Slight dependency on pseudorapidity

  3. Some information from Generator (m) • Asymmetry is nearly flat for pt (not much statistics in high pt region) • Almost flat over the detector acceptance region (e.g., |h| < 2.5)

  4. Variables to study • Production rate as a function of pt and h • Asymmetry as a function of Pt and h • Main goal : try to choose the best pdf and constrain it’s parameters • Is it really possible to choose the best pdf ? • Looked events with different existing pdf in PYTHIA first

  5. Comparison of different pdf : Generator W • There is almost no difference in rate/shape • GRV94L : Statistics is low, should have been normalised W Production rate CTEQ5L CTEQ3L CTEQ5M1 GRV94L W Asymmetry

  6. Comparison of different pdf : Generator W • There is almost no difference in rate/shape W Production rate W Asymmetry

  7. Comparison of different pdf :Generator m • There is almost no difference in rate/shape • Apparently, it is impossible to choose one pdf by rejecting others Muon Production rate Muon Asymmetry

  8. Signal and backgrounds f + fbar' -> W+/- 19.54 nb Signal • f + fbar' -> g + W+/- 24.65 nb • f + g -> f' + W+/- 21.19 nb • All these processes, where decay chains are W→τ (mnn)n~17% • f + fbar -> Z0 1.87 nb • f + fbar -> g + Z0 2.36nb • f + g -> f + Z0 1.92 nb • g + g -> t tbar ~1 nb (Yet to look) 1. Physics backgrounds : 2. Other backgrounds : • From bottom and charm decays, but associated with jets • From kaon and pion decay • Other detector backgrounds

  9. Signals for single W→µν and Rapidity of W • Isolated single muon • Global muons in CMSSW • Energy in all calorimeters due to this muon • Energy associated with the muon • Tracks associated with the muon • Large missing transverse momentum • Main difficult job is to calculate W direction from muon 4-vector . Two fold ambiguities and also need precise measurement of missing PT. • No jets Yet to have any selection criteria, but just look at those variables andexpected suggestions from you Used private sample: Gen+Sim with _1_4_5 and Digi+Reco with 1_6_0 Preselection : |h| < 1.75

  10. Event shape variables : Number of muons • No, normalisation at all, just a distribution Single W Single Z W + jet Z+ jet t→m

  11. Event shape variables : Pt of muon • Use Pt > 20 GeV and also number of muon ==1 Single W Single Z W + jet Z+ jet t→m

  12. Event shape variables : Missing Et • Use missing Et >20 GeV Single W Single Z W + jet Z+ jet t→m

  13. Event shape variables : Eta of muon Single W Single Z W + jet Z+ jet t→m

  14. Muon associated Hcal energy • Except last on all are nearly same, which is expected Single W Single Z W + jet Z+ jet t→m

  15. Tracks momentum with cone 0.5 Single W Single Z W + jet Z+ jet t→m

  16. Calorimeter energy within cone 0.5 • All are muon sample, thus all are nearly same Single W Single Z W + jet Z+ jet t→m

  17. Event shape variables : Number of jets • Why “Single W” events has more jets that “W+jet” ???? Single W Single Z W + jet Z+ jet t→m

  18. Event shape variables : Pt of jets Z+ jet Single W Single Z W + jet t→m

  19. Event shape variables : Eta of jets Z+ jet Single W Single Z W + jet t→m

  20. Summary • Why LO ‘single W’ and ‘W+q/g’ has nearly same spectrum of jet (Used default Pythia setup) • May return back to generated information • Do not expect to select the best pdf, but need to constraint those parameters for all sets. • Goal is for pdf, but if we can move fast, this analysis may also use in the initial stage of CMS run to establish the SM.

  21. Comparison of different pdf :Generator m Muon Production rate Muon Asymmetry

  22. Comparison of different pdf :Generator m • There is almost no difference in rate/shape • Apparently, it is impossible to choose one pdf by rejecting others Muon Production rate Muon Asymmetry

More Related