G X G Central Exclusive Hadron Production in CDF a.k.a. Double Pomeron Exchange, also Photoproduction Mike Albrow (Fermilab) G X G With students: Artur Swiech, Dominik Wrana, Maria Zurek (Cracow, summer students) Oleg Kuprash, Denys Lontkowski, Inna Makarenko (Kiev, students)

Central Exclusive Hadron Production Pomeron: Special strong interaction exchange, almost pure glue-initiated: What is it like? Not in PYTHIA-out-of-box or most Event Generators. p p X p p t1 X Δy Δy t2 p p p p y t-channel Rapidity Exchanges over large rapidity gaps: J or α(t) >= 1.0 And colour singlets: photon γ, pomeron IP = {gg}, odderon {ggg}? Can have γ γ (QED), γ IP (photoproduction) or IP IP (DPE) exchanges In QCD no pure {gg}, but {gg} dominates. {ggg} allowed but small, Z exchange allowed but p’s break up.

Does FSC* have anything to do with possible future HPS/AFP ? (High Precision Spectrometers for p + p  p + X + p; X = H, W+W-, etc.)? * Forward Shower Counters, tomorrow talk Indirectly YES, improving measurements of related processes t b q γ Jet H χb0 SMH(130) σ ~ 3 fb Needs high L and HPS (not FSC!) See next slide χc0 observed in CDF Level 1 triggers: GAP-μμ-GAP GAP-2EM-GAP GAP-2JET-GAP

Also measured excl: μ+μ-, J/ψ, ψ(2S), Υ, χc Central Exclusive Studies in CDF : requiring all detectors empty, incl. BSC except signal itself. IP + IP → γ + γ M(γγ) up to 20 GeV Many more candidates… result “soon” Also measured excl: μ+μ-, J/ψ, ψ(2S), Υ, χc QED γγ→e+e- M(ee) up to 75 GeV/c2 IP + IP → Jet + Jet

Exclusive M(μ+μ-) spectrum, CDF at Tevatron Not IP+IP, but γ+IP (photoproduction) J/ ψ, ψ(2S) and QED : γ γ→ μ+μ- Exclusive χc observation from J/ψ + γ KMRS: ~ 90 nb

Advert: arXiv:1006.1289 A + B  A + X + B

Old (Regge theory) New (pert. QCD) OK for H, χb, χc(?) Not for π+π-, …

1) X can be a single particle, then quantum numbers restricted Special features: 1) X can be a single particle, then quantum numbers restricted Allowed single particles: Spectroscopy, especially “glueballs” from {gg}. For (non-perturbative) … calculated as: 2) Charm: hidden and open 3) High mass multi-particle states: <nch> vs ET, jets, etc.

In IP+IP  X, Quantum numbers of X restricted. C = +1, P = +1, J = even. J = 0 at t1 ~ t2 ~ 0 (Jz = 0 rule) Single particle states: σ(600), f0(980), f0(1500), χc0, χb0 … H! Multiparticle states: 2π, 4π, φφ, ΛΛbar, etc etc. … γγ ! IP ~ {gg} and glue-rich states (“glueballs”) favoured

Old ISR data: y(π) < 1.5 2 gaps Δy = 3 If two Δy(gaps) fixed, as s goes up Δy(central) grows (& M), and σ grows. If fix two Δy(central), as s goes up Δy(gaps) grow and σ falls (~ log).

|yπ| < 1 f0(980) IGJPC = 0+0++ Angular distributions can pick out AFS: NP B264 (1986) 154 No ρ (I=1, forbidden) |yπ| < 1 f0(980) IGJPC = 0+0++ Angular distributions can pick out S-wave (J = 0) or J=1,2, etc Show S-wave dominates to 1.6 GeV ? f0(1500) IGJPC = 0+0++ Ochs & Minkowski: 300 MeV – 1700 MeV broad σ(600) glueball? (cut) (Such a state does not emerge from the interaction)

Look for ρ0ρ0 AFS: NP B264 (1986) 154 f2(1270) S-wave projection D-wave projection  J = 2 Look for ρ0ρ0 Could look for GG f2(1270)

M(K+K-) (no φ) M(K+K-) A-corrected K+K-/π+π- >~ 1 (gluey?) AFS: NP B264 (1986) 154 K+K- Acceptance M(K+K-) (no φ) M(K+K-) A-corrected K+K-/π+π- >~ 1 (gluey?) M(p-pbar)

Internal CDF Note (in preparation)

Some (selected) DPE studies of interest ~ all glue  High mass characteristics Low mass exclusives dσ/dM(ηmax) nch vs M Event shapes: Thrust T(M), Circularity Jets: 2-jets (gluon jets)…xg and DPS (2x 22) or 24 Drell-Yan & q-qbar Bose-Einstein correlations (size of π-emission region) Extremes of n(+-)/n(0) ? Limited more by effort than by topics! Anything in hadron-hadron except the very rare, & …

CDF Trigger Level 1: BSC1 CLC (both sides) Level 2 : Fwd Plug 2.1 < |η| < 3.6 (both sides) PU Both gaps Δη > 3.8, and 4.8 for tighter central |η| < 1.1 track studies. End-of-store times, mostly July 12-17 pre-shutdown, L < 50E30. Dedicated few hours. Redefining noise levels in veto regions, halo/cosmic rejection (NN). All CDF detectors “empty” for 1.1 < |η| < 5.9 both sides. (Δy > 4.8) In |η| < 1.1 : 2 Electromagnetic showers ET > 0.5 GeV 2 EM+Hadronic towers ET > 0.5 GeV 1 or 2 tracks pT > 1.5 GeV 1 “jet” ET > 3 GeV in “OR” 1000 events scanned & classified by scan. Trained NN agrees. Rate ~ 80 Hz (+0-bias)  1.6 106 GXG after clean-up:

Q1+Q2 = 0. Neither track identified as K or p by dE/dx. Exclusive 2 track events. Require calorimetry empty apart from track hits (3x3). Q1+Q2 = 0. Neither track identified as K or p by dE/dx. First quick look: Resonances f0(980), f2(1270),f0(1370) (probably) Have also candidates for exclusive K+K- & pp (dE/dx) Should have also ~12,000 2-track exclusive events Assume π+π- Above ~ 2 GeV exponential fall to ~ 6 GeV

Hidden charm (χc) and open D-Dbar pairs .. not yet, to do! CDF: dσ/dy(p + p  p + (χc) + p) = (76 +/- 10 +/- 10) nb. χc1,2,3→ J/ψ+γ not resolved July data 1.5 pb-1 … Exclusive efficiency ~ 0.25, BR(4-tracks) ~ 0.05, Efficiency ~ 0.1? Expect ~ 150 events, good mass separation between states Very clean incl. SVX χc → h+h+h-h- = 5.4% Common vertex, maximize acceptance (Si only allowed) K0S displaced vertices Expect ~ 20 – 100 exclusive pairs, need optimized search 3.8% each D0 ~10% each D+,D+S

Can we measure exclusive χc0  hadrons?

High mass data (Rapidity gaps outside stated range) Select events with anything central and gaps |η| = 1. 1 – 5.4 or 2. 1 - 5.4 Central mass distributions extend to ~ 40 GeV (60 GeV) At higher masses typically 10 – 20 charged particles How jetty? 4-jets? Circular? Any jets should be ~ pure g Exclusive JetJet?

The GXG data set gives a new (sort of) window on strong interactions (mainly non-perturbative, gluons, diffraction, pomeron structure) From a few hours of special low-L running, may expect 3 papers: IP + IP  exclusive hadron pairs, iso-scalar resonances… IP + IP  high mass, high multiplicity, jets-nojets, DPS … IP + IP  Open charm D-Dbar and hidden charm (χc) Time scale: effort dependent, maybe only Summer 2011. Therefore more data could be usefully collected and included. Have arranged to get more data (subject to other needs): If L < 50E30 and >= 1 hour left in store: Switch to dedicated GXG running If L < ~ 70E30 add GXG triggers to menu. Could get a factor ~ 5 – 10 in data (10 M events) with very little integrated luminosity. (1 hour at 50E30 = 0.18 pb-1 = 0.0002 fb-1)

How to do low-mass DPE in CMS? Cannot detect protons. With FSC can: require empty [FSC+ZDC+CASTOR+T2+HF] + Xcen (b) require [ZDC or FSC] + empty [CASTOR+T2+HF] +X FSC + ZDC HF + T2 (a) (b) HF + T2 FSC + ZDC

Summary p + p  p + G + X + G + p A key issue is always making a trigger: p’s or forward gaps (or both) Done at ISR Sqrt{s}  63 GeV with forward protons Doing it in CDF (D0?) with forwrad gaps … to come Can do in CMS especially with FSC counters to be added (ALICE too, LHCb? ….)