1 / 15

Measurement of the Inclusive Z+jet(s) Production Cross Section at CDF

Measurement of the Inclusive Z+jet(s) Production Cross Section at CDF. Oriol Salt ó IFAE – Barcelona (for the CDF Collaboration) Pheno 2007 Madison, WI. Motivation. MET + 3 jets. Boson+jets is one of the major backgrounds for MET+jets final states: t-tbar production Higgs SUSY

hila
Télécharger la présentation

Measurement of the Inclusive Z+jet(s) Production Cross Section at CDF

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 the Inclusive Z+jet(s) Production Cross Section at CDF Oriol Saltó IFAE – Barcelona (for the CDF Collaboration) Pheno 2007 Madison, WI

  2. Motivation MET + 3 jets • Boson+jets is one of the major backgrounds for MET+jets final states: • t-tbar production • Higgs • SUSY • Could be used in searches for compositeness, heavy objects decays, etc. • Test of pQCDat high momentum transfers and NLO predictions are available in some cases • It is also sensitive to Underlying Event and Hadronization modeling Z jet Pheno 2007 Madison, WI

  3. Z + jets • Z→ee + jets is a very clean signal • no missing ET • almost background free. • Z→ee + jets constitutes no background to MET+jets (SUSY signal) but allows to validate MC predictions for the rest of Z+jets and W+jets final states • Cross section is ~10 times lower than W+jets • with more than 1 fb-1 of data differential jet measurements are possible e e Z jet Pheno 2007 Madison, WI

  4. Z→ee + jets Cross Section • The measurements are performed in a well defined kinematic region • Z→ee • 66 < Mee < 116 GeV/c2 • ETe > 25 GeV • |h1e| < 1.0 |h2e| < 1.0 || 1.2 < |h2e| < 2.8 • Jets reconstructed with MidPoint algorithm with cone size R = 0.7 • pTjet > 30 GeV/c |yjet| < 2.1 DR(e,jet) > 0.7 • NLO pQCD prediction by MCFM • PDF set: CTEQ6.1M • Dynamic renormalization and factorization scale: • m2 = M2(Z) + pT2(Z) • Up to 2 jets in the final state • Rsep = 1.3 • Corrected for non-perturbative contributions Pheno 2007 Madison, WI

  5. Z + jets in hadronic collisions Calorimeter towers Unfold detector effects (detector simulation) Particles Correct for non-perturbative contributions: • Hadronization of the partons • Underlying Event (MonteCarlo simulation) Partons jet parton remnants proton anti-proton Z Underlying Event (UE) e e Pheno 2007 Madison, WI

  6. Jet Shape • The observable is sensitive to the hadronization and the Underlying Event • Very well described by the MonteCarlo simulation Pheno 2007 Madison, WI

  7. Energy flow Jet + UE • As already seen, the jet is described accurately • Also very good agreement in the part dominated by the Underlying Event Z0f=0 transverse plane calorimeter towers Dominated by the Underlying Event Pheno 2007 Madison, WI

  8. Cross Section Uncertainties CDF Run II Preliminary • The total systematic uncertainty is about 10% at low pTjet up to 15% • It is dominated by the a 3% to 14% uncertainty on the absolute jet energy scale, followed by a 5% uncertainty on the efficiency on indenifying the electrons. • Uncertainties at low pTjet are comparable to the uncertainties in the theory Pheno 2007 Madison, WI

  9. Cross Section vs. pTjet • Cross Section corrected to the hadron level • Good agreement of the NLO pQCD prediction corrected for UE and Hadronization effects. • Non-perturbative contributions up to 25% at low pTjet • Uncertainties at low pTjet are comparable to the uncertainties in the theory (10%) Pheno 2007 Madison, WI

  10. Cross Section vs. |yjet| • The cross section is also measured as a function of the jet rapidity • Good agreement with the NLO prediction • Non-perturbative contributions of ~15% Pheno 2007 Madison, WI

  11. Cross Section vs. jet multiplicity • Cross Section with respect to the inclusive number of jets • NLO predictions up to two jets in the final state • LO predictions up to 3 jets in the final state • Data supports a constant NLO/LO k-factor as a function of Njets • Non-perturbative contributions account for 15% of the cross section Pheno 2007 Madison, WI

  12. Summary • We measured the Z+jets production cross section as a function of pTjet, |yjet| and jet multiplicity • Very good agreement was found with the NLO predictions • We showed the size and importance of the non-perturbative contributions • The results will be an input for a Higgs search in the ZH(→nnbb) channel Tevatron Pheno 2007 Madison, WI

  13. Pheno 2007 Madison, WI

  14. Pheno 2007 Madison, WI

  15. Z→e+e- selection • Loose Central Electron • |h| < 1.0 • |z0| < 60 cm • pT > 10 GeV/c • ET > 25 GeV • Track quality cuts • > 3 Stereo SL w/ hits ≥ 5 • > 2 Axial SL w/ hits ≥ 5 • Iso4 – Leak < 0.1·ET • HadEm < 0.055 + 0.00045·ET • Fiduciality == 1 • Tight Central Electron • |h| < 1.0 • |z0| < 60 cm • pT > 10 GeV/c • ET > 25 GeV • Track quality cuts • > 3 Stereo SL w/ hits ≥ 5 • > 2 Axial SL w/ hits ≥ 5 • Iso4 – Leak < 0.1·ET • HadEm < 0.055 + 0.00045·ET • E/p < 2.0 OR pT < 50 GeV/c • Lshr < 0.2 • c2CES < 10.0 • -3.0 cm < Q·Dx < 1.5 cm • |Dz| < 3.0 cm • Fiduciality == 1 • Plug Electron • 1.2 < |h| < 2.8 • ET > 25 GeV • Iso4 < 4 • HadEm < 0.05 • c2PEM <= 10.0 Pheno 2007 Madison, WI

More Related