Toward triggering on hard single diffractoin in CMS Gregory Snow University of Nebraska

1. Toward triggering on hard single diffractoin in CMS Gregory Snow University of Nebraska Physics with Forward Proton Taggers at the Tevatron and LHC Manchester, 14-16 December, 2003 • Presently focusing on hard single diffraction as part of • feasibility study on rapgap triggers in CMS, with or without • proton tagging • Signature: p p p p ( Gap ) • Two or more forward di-jets, rapidity gap • accompanying proton which emits Pomeron • Context: Low-medium luminosity ( 1033 cm-2 s-1) • where there are significant bunch crossings with • a single interaction

2. POMWIG • Herwig for diffractive interactions • LANL hep-ph/0010303, 20 June 2001 for code download • and instructions • Modified deep inelastic scattering process Positron replaced by Proton Photon replaced by Pomeron Flux(xPom, t), Pomeron structure function (β, Q2) Pomeron remnant Hard scatter Proton Proton remnant • Can choose different Pomeron structure (H1, Reggeon, • user-defined) • Jets clustered at particle level with cone algorithm (R = 0.7) • Diffractive W, Higgs production available • Double Pomeron collisions also available Note: In Pomwig, the proton traveling toward negative  always emits the Pomeron in the single diffractive process

3. Jets clustered in POMWIG (cone size 0.7) are well separated from outgoing proton xPomeron < 0.02 Central and forward jets Big rapidity gap Jet axis pseudorapidity Outgoing proton sometimes seen as “jet” in POMWIG

4. Now looking at all POMWIG-generated particles in detail Fairly high particle multiplicity Navg 80 Final state event multiplicity Herwig/PDG Particle ID numbers Protons neutrons Antiprotons antineutrons Pions, kaons, etc.

5. Where are the outgoing protons which emit the Pomeron? Beam particle which emits Pomeron is Herwig’s “positron”, mostly only one in final state Number of “positrons” per event xPomeron < 0.02 Other real positrons “Positron” pseudorapidity Outgoing Protons here

6. Let’s look where some other particular final state particles go Protons Number per event xPomeron < 0.02 Pseudorapidity  Very forward proton often in diffractively produced system

7. Let’s look where some other particular final state particles go Antiprotons Number per event xPomeron < 0.02 Pseudorapidity  Few very forward antiprotons in diffractively produced system

8. Let’s look where some other particular final state particles go Pions, charged and neutral Number per event xPomeron < 0.02 Pseudorapidity  Pions extend closest to outgoing proton

9. Considering all particles, which one is closest to the outgoing proton? xPomeron < 0.03 xPomeron < 0.02 xPomeron < 0.0075  of minimum- particle per event Gap moves farther from outgoing proton for smaller xPOM

10. Considering all particles, which one is closest to the outgoing proton? Both plots xPomeron < 0.02 Energy (GeV) of minimum- particle per event HF coverage between red lines  of minimum- particle per event • Note: If one requires no hits (rapgap) in inner half of • HF (4 < || < 5), one retains 50% trigger efficiency • for xPomeron < 0.02. • Greater efficiency requires rapgap in T2/CASTOR • region (|| > 5)

11. Now shift to smaller xPomeron and observe gap to outgoing proton widen slightly Both plots xPomeron < 0.0075 Energy (GeV) of minimum- particle per event HF coverage between red lines  of minimum- particle per event • Efficiency now about 75% when requiring gap • in 4 < || < 5 inner half of HF

12. Gap in T2/Castor Gap in inner half HF and T2/Castor Gap in HF/T1 and T2/Castor • Good efficiency using gap trigger for “large” xPom • require gap in inner half of HF/T1 plus T2/Castor regions

13. 5mm HAD (143 cm) EM (165 cm) CMS Very Forward Calorimeters (HF) || = 3 || = 4 || = 5 Finely segmented, fast, scintillating fiber calorimeter

14. TOTEM T2 and CASTOR Region TOTEM T2 HF CASTOR 9,71 λI 5.4<|η|< 6.7

15. Comments and Next Steps • Particle-level output of Pomwig understood and exercised • for single hard diffraction; output topologies make sense • physically. Simulated rapgap locations matched with physical • detectors, selection efficiencies for varying kinematic ranges. • Some Next Steps • Perform full detector and trigger simulation of POMWIG • particle-level events • POMWIG generator linked to CMS simulation software • Can simulate Level-1 trigger objects output (ET per trigger • tower, etc.) • Extend study to additional processes (double Pomeron, • diffractive W/Z, Higgs, …) • Try combining gap signatures with forward proton in Roman • pots for increased power in trigger and offline • Up to what instantaneous luminosity are rapgap • signatures useful? Study gap survival vs. instantaneous • luminosity.