Tevatron Timing and Z Collision Distribution for use in the Delayed Photon Analysis

1. Tevatron Timing and Z Collision Distribution for use in the Delayed Photon Analysis Jonathan Asaadi, Adam Aurisano, Daniel Goldin, David Toback Texas A&M Universtiy (For the Delayed Photon Group) CDF SUSY Meeting 01/27/10 J.Asaadi Texas A&M

2. Outline • Brief Overview of Delayed Photon Analysis • The Importance of Collision Distributions to the Delayed Photon Analysis • Wrong Vertex and Time Biases • Understanding Background Production at Large |Z| • Accounting for Accelerator Effects • Previous work documented in CDFNote 9812 • Satellite Bunches • Conclusions / Next Steps J.Asaadi Texas A&M

3. Overview of Delayed Photon Analysis In some forms of Gauge Mediated Supersymmetry (SUSY) the next to lightest stable particle (NLSP) is long lived (lifetime on the order of nanoseconds) before decaying to a photon and the lightest stable particle (LSP). This means that you could have events where the photons arrive late when compared to expectation from prompt photons (“delayed photons”) • An earlier study found an excess in the exclusive Photon + MET sample • Photon ET > 45 GeV • MET > 45 GeV • Veto Jet ET > 15 GeV • Veto Lepton ET > 10 GeV Previous study assumed that the backgrounds were symmetric around t = 0. Our Preliminary Studies are showing this in not a good assumption

4. Collision Distribution • A process can be biased towards large Z in the delayed photon analysis for numerous reasons: • Electrons coming from large Z are more likely to fake a photon • Photons identified with a wrong vertex are more likely to have their Et ‘promoted’ • Photon + Jet production at large Z can when the jet goes down the beam pipe and a wrong vertex is selected (Delayed Photon + MET) If a physics process is biased to large Z this can bias us to larger times At larger Z we are likely to select the wrong vertex in the first place

5. Collision Distribution Some of these effects have been demonstrated in Wrong Vertex events using W  en data and Monte Carlo sample MC Data Understanding collision distributions at large Z are important for our different background sources See SUSY Talks: Asaadi 10/09 and Aurisano 09/09

6. Background Production at Large Z SVX Bulkheads Currently running higher statistic MC to update this sample Monte Carlo studies show that for Wrong Vertex Events large Z Vertex becomes very important Do we understand and model our beam and how it impacts our collision distributions at large Z?

7. See CDFNote 9812 Accelerator Effects This changes our understand -ing of the modeling of our collision distributions The longitudinal profile (sp) for the protons and antiprotons becomes wider during the course of a store The rate of events @ z = -100 cm with a collision time of 5 ns rises by a factor of 100 which means there are more collision out at high Z that could fake events with a large time

8. Satellite Bunches Other accelerator effects that could influence the collision distributions The Radio Frequency (RF) Cavities used in the Tevatron to capture and accelerate the proton and anti-proton bunches create satellite bunches with ½ RF Cavity time at ~ 1% the main bunch intensity. We want to understand how taking these satellite bunches into account in our modeling of the beam can effect the collision Z and time distribution at large distances from the center of the detector J.Asaadi Texas A&M

9. Satellite Bunches Collision Time vs. Collision Z w/ Satellites Collision Time vs. Collision Z w/o Satellites J.Asaadi Texas A&M

10. Satellite Bunches Main Bunch / Satellite Bunch Interaction SatelliteBunch / Satellite Bunch Interaction

11. Satellite Bunches @ z = -100 cm Taking into account the satellite bunch changes the mean and RMS Main Bunch/Satellite Bunch interaction increases the number of events coming from z = -100 w/ t = 5 ns How big of an effect is the satellite bunch interactions ?

12. Satellite Bunches Insert ratio plots: Main/Main divided by the denominator plot. Main/Satellite divided by the denominator plot Satellite/Satellite divided by the denominator plot J.Asaadi Texas A&M

13. Satellite Bunches J.Asaadi Texas A&M

14. Conclusions / Next Steps

15. Satellite Bunches Collision Distribution w/ Satellite Distributions Collision Distribution w/o Satellite Distributions Collision Distributions are altered by taking into account the satellite bunches at high Z and large time Which interactions are causing this alteration? Main Bunch/Main Bunch, Main Bunch/Satellite Bunch, Satellite Bunch/Satellite Bunch J.Asaadi Texas A&M

16. Satellite Bunches Near the center of the detector Main Bunch/Main Bunch and Satellite Bunch/Satellite Bunch dominate Collision Distribution Main/Main Bunch Collision Distribution Main/Satellite Bunch Collision Distribution Satellite/Satellite Bunch At large Z Main Bunch/Satellite Bunch becomes important J.Asaadi Texas A&M

17. Satellite Bunches Near the center of the detector Main Bunch/Main Bunch and Satellite Bunch/Satellite Bunch dominate Collision Distribution Main/Main Bunch Collision Distribution Main/Satellite Bunch Collision Distribution Satellite/Satellite Bunch At large Time Main Bunch/Satellite Bunch and Satellite Bunch/Satellite Bunch becomes important J.Asaadi Texas A&M