CDF Paper Seminar October 23 2003 Inclusive Double-Pomeron

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CDF Paper Seminar October 23, 2003. Inclusive Double-Pomeron Exchange at the Fermilab Collider Authors : M. E. Convery, K. Goulianos, K. Hatakeyama The Rockefeller University Godparents : Andrey Korytov, Giorgio Bellettini, Mario Martinez-Perez PRL Draft : CDF Note 6568 1

History of the Analysis ¡ ¡ Analysis blessed on May 2, 2002 and May 16, 2003. PRL Draft : CDF Note 6568 Comments from l University of Toronto group l UC Davis group l University of Illinois group l Universita di Padova group Many Thanks! Main Analysis Document : CDF Note 5865 Analysis Web Page : http: //wwwcdf. fnal. gov/internal/people/links/Kenichi. Hatakeyama /idpe. html October 23, 2003. Kenichi Hatakeyama 2

$High Energy Particle Diffraction ¡ ¡ Several of our collaborators have expressed an unfamiliarity$

High Energy Particle Diffraction ¡ ¡ Several of our collaborators have expressed an unfamiliarity with diffractive physics. This talk will start with a brief introduction to diffraction at CDF. Details may be found in textbooks such as this. Also, “Diffractive interactions of hadrons at high energies”, K. Goulianos, Phys. Rep. 101, 169 (1983) would be helpful for understanding the basics of soft hadron-hadron diffraction. October 23, 2003. Kenichi Hatakeyama V. Barone, E. Predazzi, Springer Press, 2002. 3

$Introduction Diffraction in high energy hadron physics refers to a reaction in which no$

Introduction Diffraction in high energy hadron physics refers to a reaction in which no quantum numbers are exchanged between colliding particles. Shaded Area : Region of Particle Production October 23, 2003. Kenichi Hatakeyama 4

$CDF Publications on Diffraction in Run 1 Soft Diffraction Single Diffractive (SD) Double Diffractive$

CDF Publications on Diffraction in Run 1 Soft Diffraction Single Diffractive (SD) Double Diffractive (DD) Double Pomeron Exchange (DPE) Single+Double Diffractive (SDD) PRD 50 (1994) 5535 PRL 87 (2001) 141802 This paper! PRL 91 (2003) 011802 Hard Diffraction (diffraction +hard scattering) Single Diffractive (SD) Jet-Gap-Jet W: PRL 78 (1997) 2698 Dijets + Roman Pots PRL 74 (1995) 855 Dijet : PRL 79 (1997) 2638 PRL 84 (2000) 5043 PRL 80 (1998) 1156 b-quark: PRL 84 (2000) 232 PRL 88 (2002) 151802 PRL 81 (1998) 5278 J/ψ : PRL 87 (2001) 241802 October 23, 2003. Kenichi Hatakeyama Double Pomeron Exchange (DPE) Dijet : PRL 85 (2000) 4217 5

$What did we learn from hard ND diffraction? For SD dijet production, Main issue$

What did we learn from hard ND diffraction? For SD dijet production, Main issue in hadronic diffraction : ¡ ¡ Do hard diffraction processes obey QCD factorization? (Are the diffractive parton distribution functions universal? ) SD This question can be addressed by comparing the functions extracted from different processes. October 23, 2003. Kenichi Hatakeyama 6

$Main Issue in Hadronic Diffraction : Results from single diffractive (SD) dijet production CDF$

Main Issue in Hadronic Diffraction : Results from single diffractive (SD) dijet production CDF Collaboration, Phys. Rev. Lett. 84, 5043 -5048 (2000). ¡ The diffractive structure function measured using SD dijet events at the Tevatron is smaller than that at HERA by approximately an order of magnitude. Factorization Breakdown ~10 Next Q : How is it broken? ¡ The discrepancy is generally attributed to additional color exchanges which spoil the “diffractive” rapidity gap. October 23, 2003. Kenichi Hatakeyama 7

Dijet Production in DPE CDF Collaboration, Phys. Rev. Lett. 85, 4215 -4220 (2000). ¡ ¡ Dijet production by double pomeron exchange was studied by CDF. R[DPE/SD] is larger than R[SD/ND] by a factor of about 5. The formation of the 2 nd gap is not as suppressed as the 1 st gap. Extract diffractive structure function from R[DPE/SD] and compare it with expectations from HERA results. October 23, 2003. Kenichi Hatakeyama 8

$Diffractive Structure Function measured using DPE dijet events The diffractive structure function measured using$

Diffractive Structure Function measured using DPE dijet events The diffractive structure function measured using DPE dijets is approximately equal to expectations from HERA! October 23, 2003. Kenichi Hatakeyama Factorization holds? 9

$Soft Diffraction : Regge Theory Single Diffractive Cross Section σtot (mb) Total Cross Section$

Soft Diffraction : Regge Theory Single Diffractive Cross Section σtot (mb) Total Cross Section October 23, 2003. √s (Ge. V) Kenichi Hatakeyama 10

$Soft Diffraction : Inclusive (Soft) SD Results ¡ ¡ Unitarity problem : The measured$

Soft Diffraction : Inclusive (Soft) SD Results ¡ ¡ Unitarity problem : The measured SD cross section is smaller than the Regge theory prediction by approximately an order of magnitude at the Tevatron energy. Normalizing the integral of the pomeron flux (f. IP/p) to unity yields the correct √s-dependence of σSD. Tevatron data Renormalization K. Goulianos, PLB 353, 379 (1995). Similar results were obtained for double diffraction as well. Is the formation of the second gap suppressed? October 23, 2003. Kenichi Hatakeyama Study DPE 11

Inclusive (Soft) DPE Cross Section ξp , tp Regge theory prediction + factorization : = g: triple-Pomeron coupling, κ=g/β(0). Flux renorm. model : (both gaps are suppressed. ) K. Goulianos, Phys. Lett. B 353, 379 (1995). Gap probability (Pgap) renorm. model : Pgap is renormalized. (only one gap is suppressed. ) K. Goulianos, e. g. hep-ph/0110240 (2001). October 23, 2003. Kenichi Hatakeyama 12

Analysis Strategy ¡ ¡ ¡ Use events triggered on a leading antiproton. ξpbar is measured by Roman Pots : ξpbar. RPS. Measure ξp (ξpbar) from BBC and calorimeters : ξp. X (ξpbar. X). Calibrate ξX by comparing ξpbar. RPS and ξpbar. X. Plot ξp. X distribution and look for a DPE signal expected in the small ξp. X region. October 23, 2003. Kenichi Hatakeyama 13

Roman Pot Spectrometer Roman Pots detect recoil antiprotons October 23, 2003. Kenichi Hatakeyama 14

Reconstruction of ξp. X Calorimeters • Cannot reconstruct ξp by RPS. • Use calorimeter towers and BBC hits to reconstruct ξp : (J. Collins, hep-ex/9705393) The CAL+BBC method allowed us to access all the way down to the kinematic limit. Calorimeters : use ET and η of towers above noise level. BBC : use hits in BBC scintillation arrays. l BBC p. T is chosen to follow the “known” p. T spectrum : October 23, 2003. Kenichi Hatakeyama 15

Data Sample and Event Selection ¡ ¡ Roman Pot triggered data collected in 1800 Ge. V low luminosity runs during Run 1 C (<Linst> ~ 0. 2 x 1030 cm-2 s-1). Overlap event (containing SD + additional ND collisions which kill the rapidity gap signal ) rate is low (~4% ~0. 5% after the cuts shown below). Selection Cut Total Number of vertices ≤ 1 |zvtx| ≤ 60 cm (if there is one) 1 MIP in the RP trigger counters 1 or 2 reconstructed tracks in RPS West BBC multiplicity ≤ 6 October 23, 2003. Kenichi Hatakeyama Number of Events 1200779 1123407 1058876 971749 763268 660240 568478 16

Monte Carlo Event Generation : MBR (CDF Note 0256, 0675, 5371. PRD 50 (1994) 5535, 5550. ) SD and DPE event generation MBR min-bias MC: ¡ ¡ Specially designed to reproduce soft-interaction results from low-energy experiments Used to determine CDF total, SD and DD cross sections [PRL 50 (1994) 5535, 5550, PRL 87 (2001) 141802. ] Detector simulation Calorimeters: not well calibrated for low p. T particles. Convert the generated particle p. T to the calorimeter ET using calibrations determined specifically for low-p. T particles. BBC: assume that all charged particles will trigger the BBCs. October 23, 2003. Kenichi Hatakeyama 17

Calibration of ξX ξX distribution in every ξRPS bin is fitted to P 1 : Peak P 2 : Width ξX = ξRPS, (ξX is calibrated so that ξX = ξRPS. ) P 2/P 1 = 0. 57 (ξX resolution is ~60%. ) October 23, 2003. Kenichi Hatakeyama 18

ξp. X Distribution ¡ ¡ ¡ The input ξp distribution in DPE MC is 1/ξp 1+ε (ε = 0. 104 is obtained from p±p/π±p/K±p total cross sections). The DPE and SD MC distributions are independently normalized to the data distribution. The measured ξp. X distribution is in agreement with the DPE+SD MC distribution. October 23, 2003. Kenichi Hatakeyama 19

ξp. X Distribution ¡ ¡ ¡ The ξp distribution on the previous page shows “number of events per Δlogξ=0. 1”; Multiply each bin by 1/ξ to show d. N/dξ. A diffractive peak of 3 orders of magnitude is observed! October 23, 2003. Kenichi Hatakeyama 20

Corrections to R[DPE/SD(incl)] : ¡ ξp. X resolution : l l ¡ According to MC, more events with ξp>0. 02 seem to fall into ξp. X<0. 02 than events with ξp<0. 02 fall into ξp. X>0. 02. R[DPE/SD(incl)] is corrected by Fresol=1. 04± 0. 04 Low ξpbar. X enhancement: l l l 3~4 % of events have very low ξpbar. X values although those events have 0. 035< ξpbar. RPS <0. 095. MC shows a similar effect, but not as pronounced as in data. Obtain R[DPE/SD(incl)] with/without ξpbar. X<0. 003 cut, and take the average. October 23, 2003. Kenichi Hatakeyama 21

Systematic Uncertainties Source ξp. X calibration Estimator Change ξp. X by 10 % Uncertainty 0. 003 (2%) ξp. X resolution Whole correction 0. 008 (4%) Low ξpbar. X enhancement Half of the variation 0. 008 (4%) Total 0. 012 (6%) The measured fraction is in agreement with the prediction from the renormalized gap probability model (0. 21± 0. 02)! October 23, 2003. Kenichi Hatakeyama 22

Comparisons with phenomenological models Source Data R[DPE/SD(incl)] 0. 195± 0. 001± 0. 010 Regge 0. 36± 0. 04 Flux Renormalization 0. 041± 0. 004 Pgap Renormalization 0. 21± 0. 02 In agreement with the renormalized gap predictions! October 23, 2003. Kenichi Hatakeyama 23

Proton Dissociation Events Our “DPE” signal actually consists of two classes of events; Events in which both the proton and antiproton escape intact from the collision typically called “DPE”. Events in which the antiproton escapes intact from the collision, while the proton dissociates into a small mass cluster Y (MY 2 <~8 Ge. V 2) proton dissociation events. ¡ ¡ Particles in Y have rapidity up to y=7. 5. DPE In 35% of events (“A”), east BBC covers up to η=5. 9, Weighted average : MY 2 < e 7. 5 - 5. 9 = 5 Ge. V 2. 8 Ge. V 2 In 65% of events (“B”), east BBC covers up to η=5. 2, MY 2 < e 7. 5 - 5. 2 = 10 Ge. V 2. R[DPE/SD(incl)] is larger in “B” than in “A” by 6%. The contribution of proton dissociation events with 1. 5<MY 2<8 Ge. V 2 to R[DPE/SD(incl)] is October 23, 2003. ~15%. Kenichi Hatakeyama Proton dissociation event All the particles in Y go beyond BBC so that the event is indistinguishable from “DPE” events. 24

$Gap Fraction σ (mb) Soft Diffraction : Summary October 23, 2003. Good Agreement with$

Gap Fraction σ (mb) Soft Diffraction : Summary October 23, 2003. Good Agreement with Renormalized Gap Predictions! SD DPE Kenichi Hatakeyama DD SDD 25

Summary ¡ ¡ ¡ We have observed double pomeron exchange events in an inclusive single diffractive event sample. The measured ξp. X distribution exhibits ~1/ξ 1+ε behavior (ε = 0. 104). The measured DPE fraction in SD is : for 0. 035 <ξpbar< 0. 095, |tpbar|<1 Ge. V 2, ξp. X< 0. 02 and MY 2<~8 Ge. V 2 at √s = 1800 Ge. V, Ø in agreement with the renormalized gap prediction. In events with a rapidity gap, the formation of a second gap is “unsuppressed”! Consistent with results from hard diffraction Universality of the rapidity gap formation October 23, 2003. Kenichi Hatakeyama 26

$Summary + Ø Universality of rapidity gap formation across soft and hard diffraction processes.$

Summary + Ø Universality of rapidity gap formation across soft and hard diffraction processes. Ø Events with multiple rapidity gaps can be used to eliminate the “suppression” factor… Facilitate QCD calculation of hard diffraction. The diffractive structure function measured using DPE dijets is approximately equal to expectations from HERA! October 23, 2003. Kenichi Hatakeyama 27

Backups October 23, 2003. Kenichi Hatakeyama 28

$Regge Theory & Factorization Single Diffractive Cross Section Total & EL Cross Sections October$

Regge Theory & Factorization Single Diffractive Cross Section Total & EL Cross Sections October 23, 2003. Kenichi Hatakeyama 29

$Unitarity Problem Single Diffractive Cross Section Total Cross Section [ε=0. 104 in PLB 389$

Unitarity Problem Single Diffractive Cross Section Total Cross Section [ε=0. 104 in PLB 389 (1996) 176] The ratio σDPE/σSD reaches unity at √s~2 Te. V. In data, s 2ε in dσSD/d. M 2 1 October 23, 2003. Kenichi Hatakeyama 30

$Soft Single Diffraction Results KG&JM, PRD 59 (1999) 114017 dσSD/d. M 2 ¡ ¡$

Soft Single Diffraction Results KG&JM, PRD 59 (1999) 114017 dσSD/d. M 2 ¡ ¡ KG, PLB 358 (1995)379 σSDtot versus √s Differential cross section agrees with Regge predictions (left) Normalization is suppressed by flux factor integral (right) October 23, 2003. Kenichi Hatakeyama 31

$Renormalization Single Diffractive Cross Section In data, s 2ε 1 Renormalization K. Goulianos, Phys.$

Renormalization Single Diffractive Cross Section In data, s 2ε 1 Renormalization K. Goulianos, Phys. Lett. B 358 (1995) 379 October 23, 2003. Kenichi Hatakeyama 32

$Soft Double Diffraction Results CDF, Phys. Rev. Lett 87 (2001) 141802 dσDD/dΔη 0 ¡$

Soft Double Diffraction Results CDF, Phys. Rev. Lett 87 (2001) 141802 dσDD/dΔη 0 ¡ ¡ σDDtot versus √s Differential cross section agrees with Regge predictions (left) Normalization is suppressed by flux factor integral (right) October 23, 2003. Kenichi Hatakeyama 33

Past Experimental Results : UA 8 Collaboration NLB 514 (1998) 3, PLB 481 (2000) 177, EPJC 25 (2002) 361. Extracted σIPIPtot using FIP/p(ξ, t) from their SD analysis. ¡ Ø The extracted σIPIPtot shows an enhancement at low MX. They attributed it to the glueball production. . . Note : If the standard ε~0. 1 is used, the enhancement is reduced significantly. But, the extracted σIPIPtot is overall higher than the expectation. October 23, 2003. Consistent with our results Kenichi Hatakeyama 34

Beam-Beam Counters In 35% of events (“A”), East BBC West BBC East BBC ¡ West BBC Red : Dead Channels Light blue : Channels used to reconstruct ξX ¡ In 65% of events (“B”), October 23, 2003. Kenichi Hatakeyama 35

Reconstruction of ξp. X : BBC Use calorimeter towers and BBC hits to reconstruct ξX, BBC (ξp. BBC) : use hits in BBC scintillation arrays Ø Ø Ø use only inner 3 (shaded) layers (the most-outer layer overlaps with the forward cal). p. T is chosen to follow the “known” p. T spectrum η is chosen randomly within the η range of the BBC counter which has a hit. October 23, 2003. Kenichi Hatakeyama 36

Reconstruction of ξp. X : Calorimeter (ξp. CAL) : use ET and η of towers above the noise level ξp. CAL has to be corrected for Ø Ø Calorimeter non-linearity at low ET region Particles below the applied ET threshold The correction factor for ξCAL is obtained so that ξX(median): ξRPS=1: 1. October 23, 2003. Kenichi Hatakeyama 37

ξX Calibration : ξpbar. X distributions in 9 ξpbar. RPS intervals ξX distribution in every ξRPS bin is fitted to P 1 : Peak, P 2 : Width • ξX(median) = 0. 94 ξRPS calibrated later to obtain ξX(median)=ξRPS • P 2/P 1 = 0. 57 (ξX resolution is ~60%. ) October 23, 2003. Kenichi Hatakeyama 38

ξpbar. X Distribution We calibrated ξX so that ξX(median) : ξRPS becomes 1 : 1. The choice of P 1/median/mean does NOT make a difference in R[DPE/SD(incl)], since the choice is taken into account by the ξX resolution correction, Fresol. October 23, 2003. Kenichi Hatakeyama 39

BBC Multiplicities in MC “A” q q q “B” The peak at EBBC=0 in data distributions is due to DPE events. The MBR SD MC whose d. N/dη is already checked in PRD 50 (1994) 5535, shows much lower multiplicities in the east BBC. The higher BBC multiplicities in data are presumably due to “splashes” which are hard to simulate. In SD MBR, for east BBC hits, don’t use the information of particles generated by MBR but simulate east BBC hits according to the data east BBC multiplicities. October 23, 2003. Kenichi Hatakeyama 40

BBC Contribution to ξX (A) October 23, 2003. Kenichi Hatakeyama (B) 41

ξp. X resolution correction ¡ ¡ Generate ξ by using dσ/dξ from l F. Abe et al. , PRD 50 (1994) 5535. l K. Goulianos & J. Montanha, PRD 59 (1999) 114017. Smear ξ according to the form: - P 2/P 1 = 0. 57, P 1 = 0. 67ξ (P 1 = 0. 67 xmedian when P 2/P 1=0. 57) Ø The number of events with ξ<0. 02 increases about 4% after the smearing. October 23, 2003. Fresol=1. 04± 0. 04 Kenichi Hatakeyama 42

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