1 / 23

Diffractive W and Z Production at Tevatron

Diffractive W and Z Production at Tevatron. Konstantin Goulianos The Rockefeller University and the CDF collaboration. Moriond QCD and High Energy Interactions La Thuile, Italy March 14th - March 21st 2009. Contents. Introduction Diffractive W / Z Exclusive Z search Summary.

liberty-preston
Download Presentation

Diffractive W and Z Production at Tevatron

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. Diffractive W and Z Production at Tevatron Konstantin Goulianos The Rockefeller University and the CDF collaboration Moriond QCD and High Energy Interactions La Thuile, Italy March 14th - March 21st 2009

  2. Contents • Introduction • Diffractive W / Z • Exclusive Z search • Summary DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  3. Diffraction and Exclusive Production at CDF Diffraction and Exclusive Production at CDF soft and hard topologies studied Double Pomeron Exchange (DPE) Single Diffraction dissociation (SD) Double Diffraction dissociation (DD) Single + Double Diffraction (SDD) JJ, ee, mm, gg exclusive p p JJ, b, J/y,W DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  4. recoil p or rap-gap MX p’ p’ diffractive signature p p MX x,t dN/dh rap-gap x=Mx2 /s Dh=-lnx h 0 DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  5. e g* p p p p p KG, PLB 358 (1995) 379 Breakdown of factorization CDF hard CDF soft ZEUS and H1 vs. CDF sTsd ~ 8 HERA H1 ZEUS ~8 CDF same suppression factor in soft and hard diffraction  gap survival responsible for suppression DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  6. CDF hard diffraction fractions Fraction: R≡SD/ND ratio @ 1800 GeV Fraction (R) % JJ 0.75 +/- 0.10 W 0.115 +/- 0.55 b 0.62 +/- 0.25 1.45 +/- 0.25 J/y JJ, W, b, J/y dN/dh • All fractions ~ 1% • (differences due to kinematics) • ~ uniform suppression • ~ FACTORIZATION ! FACTORIZATION ! h  suppression due to gap survival DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  7. DIFFRACTIVE W / Z PRODUCTION • LO diagrams • Motivation • CDF II detectors  miniplugs  measurements W/miniplugs  dynamic alignment • Analysis  selection requirements  reconstructed diffractive W mass  rejection of multiple interactions • Diffractive W / Z results DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  8. p p IP W, Z p Diffractive LO W/Z diagrams p p IP W, Z p • Diffractive W production probes the quark content of the Pomeron • To leading order, the W is produced by a quark in the Pomeron • Production by gluons is suppressed by a factor of aS, and can be distinguished from quark production by anassociated jet DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  9. Diffractive W/Z - motivation • In Run I, combining diffractive dijet production with diffractive W production was used to determine the quark/gluon content of the Pomeron === • In Run II, we aim at determining the diffractive structure function for a more direct comparison with HERA. • To accomplish this we use: • New forward detectors • New methodology • More data Phys Rev Lett 78, 2698 (1997) Fraction of W events due to SD Rw=[1.15±0.51(stat)±0.20(syst) ]% for x<0.1 integrated over t DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  10. The CDF II detectors ~56 m Roman Pot Spectrometer  RPS RPS acceptance ~80% for 0.03 < x< 0.1 and |t| < 0.1 DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  11. The MiniPlugs @ CDF DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  12. MP TOWER STRUCTURE Measurements w/the MiniPlugs MULTIPLICITY @ POSITION ENERGY • ADC counts in MiniPlug towers • in a pbar-p event at 1960 GeV. • “jet” indicates an energy cluster • and may be just a hadron. • 1000 counts ~ 1 GeV NIM A 430 (1999) NIM A 496 (2003) NIM A 518 (2004) Multiplicity of SD and ND events DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  13. Dynamic Alignment of RPS Detectors Method: iteratively adjust the RPS X and Y offsets from the nominal beam axis until a maximum in the b-slope is obtained @ t=0. Limiting factors 1-statistics 2-beam size 3-beam jitter @ CDF W/lowlum data DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  14. Diffractive W/Z analysis • Using RPS information: • No background from gaps due to multiplicity fluctuations • No gap survival probability problem • The RPS provides accurate event-by-event x measurement • Determine the full kinematics of diffractive W production by obtaining hnusing the equation: where This allows determination of: • W mass • xBj • Diffractive structure function DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  15. W/Z selection requirements Standard W/Z selection Diffractive W/Z selection • RPS trigger counters - MIP • RPS track - 0.03< x <0.10, |t|<1 • W 50< MW(xRPS,xcal) < 120 • Z  xcal < 0.1 DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  16. Reconstructed Diffractive W-Mass CDF W mass (press release 2007): 80,413 +/- 48 MeV/c2 DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  17. Rejection of Multiple Interactions ND Z w/soft SD overlap ND W w/soft SD overlap Zeeor mm Wen or mn • xRPS>xCAL effective in rejecting overlaps in W case  cannot be applied in Z case (no missing n) DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS 17

  18. Diffractive W/Z results RW (0.03 < x< 0.10, |t|<1)= [0.97 ± 0.05(stat) ± 0.11(syst)]% Run I: RW =1.15±0.55 % for x<0.1 estimate 0.97±0.47 % in 0.03 < x < 0.10 & |t|<1 RZ (0.03 < x< 0.10, |t|<1)= [0.85 ± 0.20(stat) ± 0.11(syst)]% CDF/DØ Comparison – Run I (x < 0.1) • CDF PRL 78, 2698 (1997) • Rw=[1.15±0.51(stat)±0.20(syst)]% • w/gap acceptanceAgap=81% • (from MBR/PYTHIA Monte Carlo) • uncorrected forAgap: • Rw=(0.93±0.44)% • RZ =? (not measured in Run I) • DØ Phys Lett B 574, 169 (2003) • Rw=[5.1±0.51(stat)±0.20(syst)]% • w/gap acceptanceAgap=(21±4)% • (model dependent) • uncorrected for Agap :RW=[0.89+0.19-0.17 ]% RZ=[1.44+0.61-0.52 ]% stay tuned for results on FDW/Z DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  19. Fermilab result of the week Thursday, March 12 2009 DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  20. Exclusive Z /   llstudies* Exclusive Z SM cross section: 0.3 fb [Motyka & Watt]1 1.3 fb[Goncalves & Machado]2 Expect ~0.6 - 2.6 events in 2 fb-1 (not including 3.37% leptonic BF). Search for BSM physics, e.g. color sextet quark model3: much enhanced cross section expected. ee or mm 1 Phys. Rev. D78, 014023 (2008) 2 Eur. Phys. J., C56 33 (2008) 3 Phys. Rev. D72,036007 • Exclusive di-lepton cross section: • Background to exclusive Z • Can be used to calibrate forward proton detectors:  = s-1/2 pTle-l ee or mm * see Emily Nurse http://www.fp420.com/conference/dec2008/index.html DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  21. Exclusive z /   ll results L= 2.20 (2.03) fb-1 in the electron (muon) channels • e+e- or +- with pT > 25 GeV • |1| < 1.0, |2| < 1.5 • |e1| < 1.3, |e2| < 3.6 • require 82 < Mll< 98 GeV W  l  events used as a control to study exclusivity cuts CDF Run II Preliminary Exclusive Z (Zexcl)< 0.96 pb @ 95% C.L. SM: 0.3 fb [Motyka & Watt] 1.3 fb [Goncalves & Machado] Exclusive di-leptons  (ppp l l p) = 0.24pb Mll > 40 GeV, |l| < 4.0 [LPAIR prediction:  = 0.256 pb] +0.13 - 0.10 DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  22. SUMMARY • Overview of diffraction at CDF • Breakdown of factorization – HERA vs. Tevatron • CDF hard diffraction fractions ~1 % – factorization? • Gap survival responsible for suppression • Diffractive W/Z with Roman Pot Spectrometer tagging • W diffractive fraction in agreement with Run I • W and Z diffractive fractions are equal within error • Exclusive Z production – (Zexcl)< 0.96 pb @ 95% C.L. (~ 1 fb expected in the SM) RW (0.03 < x < 0.10, |t|<1)= [0.97 ± 0.05(stat) ± 0.11(syst)]% RZ (0.03 < x < 0.10, |t|<1)= [0.85 ± 0.20(stat) ± 0.11(syst)]% DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

  23. thank you thank you DIFFRACTIVE W AND Z PRODUCTION @ TEVATRONK. GOULIANOS

More Related