1 / 38

Saturation, Low-x, and QCD at RHIC, Part 4 Future Perspectives (near and long term)

Saturation, Low-x, and QCD at RHIC, Part 4 Future Perspectives (near and long term). T. Hallman Villaggio Guglielmo, Italy. Overview of forward-tagged proton program. The physics program of tagged forward protons with STAR at RHIC in addition to the elastic scattering will:

bsimpson
Télécharger la présentation

Saturation, Low-x, and QCD at RHIC, Part 4 Future Perspectives (near and long term)

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. Saturation, Low-x, and QCDat RHIC, Part 4Future Perspectives (near and long term) T. Hallman Villaggio Guglielmo, Italy TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  2. Overview of forward-tagged proton program The physics program of tagged forward protons with STAR at RHIC in addition to the elastic scattering will: • Study standard both elastic and inelastic hadron diffraction and its spin dependence in unexplored t and s range. • Study the structure of color singlet exchange in the non-perturbative regime of QCD. • Search for central production of light and massive systems in double Pomeron exchange process -glueballs, hybrids. • Search for anOdderon - an eigenstate of CGC. There is a great potential for important discoveries beginning with the next RHIC run (November 2007) TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  3. Gluon Ladders Gluonic Exchanges PQCD Picture In terms of QCD, Pomeron exchange consists of the exchange of a color singlet combination of gluons. Triggering on forward protons at high energies predominantly selects such exchanges and hence interactions mediated by gluon matter. TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  4. A new QCD exploration at RHIC Forward Tagged Proton Studies in STAR Polarized proton-proton Elastic Scattering (pp pp) • The instrumentation used will be the STAR detector and the Roman Pots of the pp2pp experiment • The pp2pp Roman Pot detectors will be used to tag very forward protons, thus selecting processes in which the proton stays intact, and the exchange has quantum numbers of the vacuum,so called Pomeron (IP) exchange. (For these events, the probability of measuring reactions where colorless gluonic matter dominates the exchange is enhanced). • The use of polarized proton beams, unique at RHIC, will allow exploring unknown spin dependence of diffraction including both elastic and inelastic processes. • As the entire energy range of this study has been inaccessible to proton-proton (elastic) scattering in the past, all results will be new results. TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  5. A new QCD exploration at RHIC Spin averaged observables • Measurement of the differential pp cross section ds/dt over extended t-range will include the region at lower |t| that is particularly sensitive to the r-parameter: measurements will include: 1) the r-parameter; 2) the nuclear slope parameter b in a combined fit to the differential cross section, and 3) the total cross section stot. • Interest in such studies: an asymptotic difference observed between the differential and total cross sections for pp could indicate an Odderon contribution to the scattering amplitude. (absence of an Odderon contribution would lead to identical cross sections); measurement of the total cross section, stot , at the highest possible energy will also probe the prevalent assumption that the cross sections for pp and pp scattering are asymptotically identical. • With the expected 20106 elastic events the estimated error on the slope parameter is Db=0.31 (GeV/c)-2 and that for the ratio of the real to imaginary part, Dr=0.01. This is comparable to the precision for existing measurements from pp and pp data. The Dstot = 2-3 mb. TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  6. A new QCD exploration at RHIC Spin dependent observables • By measuring spin related asymmetries one will be able to determine elastic scattering at the amplitude level. The availability of longitudinal polarization will allow measuring ALL in addition to ANN, ASS, and AN resulting in a significant improvement of the scientific reach of these measurements. • Physics motivation to measure AN : possibility of the rise with energy of the spin-flip to spin-nonflip amplitudes ratio ( it may occur that the small contribution from hadronic spin-flip to the spin single-spin asymmetry observed with a polarized jet target at 100 GeV/c could be increased at s=200 GeV). • Reaching small |t|-values will allow measurement of the single spin analyzing power AN close to its maximum at |t| =0.0024 (GeV/c)2, where Amax = 0.04, at s = 200 GeV. The AN and its t-dependence in the covered range are sensitive to a possible contribution of the single spin-flip amplitude, f5, from the interference between the hadronic spin-flip amplitude with the electromagnetic non-flip amplitude. • An additional contribution of the hypothetical Odderon to the pp scattering amplitude can be probed by measuring the double spin-flip asymmetry, ANN. (ANN is thought to be sensitive to contributions of the real and imaginary parts to the double spin-flip amplitude, f2, in the range 0.003 < |t| < 0.010 (GeV/c)2). TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  7. Central Production in Double Pomeron Exchange For each proton vertex one has t four-momentum transfer p/p MXinvariant mass In the double Pomeron exchange process each proton “emits” a Pomeron and the two Pomerons interact producing a massive system MX where MX =  c(b), qq(jets), H(Higgs boson), gg(glueballs) The massive system could form resonances. We expect that because of the constraints provided by the double Pomeron interaction, glueballs, hybrids, and other states coupling preferentially to gluons, will be produced with much reduced backgrounds compared to standard hadronic production processes. TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  8. A new QCD exploration at RHIC Central production of glueballs • The production of glueballs may be enhanced in the central region in the process pp pMXp.The crucial argument here is that the pattern of resonances produced in the central region, where both forward protons are tagged, depends on the vector difference of the transverse momentum of the final state protons kT1, kT2, with dPTkT1kT2. The so-called dPT filter argument is that when dPT is large (LQCD) qbar-q states are prominent and when dPT is small, the surviving resonances include glueball candidates. The geometrical acceptance of the proposed setup for both SDD and DPE processes, generating protons with t and  uniformly distributed in the regions 0.003< |t|< 0.04 and 0.005 <  < 0.05 respectively. • In the proposed research, large data samples of diffractive states can be obtained and analyzed as a function of diffractive mass and t (d2σ/dMX2dt) for central production. As noted above, when dPT between two out going protons is small, the fraction of glueball candidates is enhanced; when the dPT is big the qqbar states are enhanced. In quantifying the threshold between these regimes, the WA102 experiment [54] found "small" to be dPT < 0.2 GeV and "big" to be dPT > 0.5 GeV. • With the expected luminosity one can collect about 450,000 triggered DPE events during the three days of running, with 40 hrs of useful beam time. The search for glueballs remains an experimental question.. TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  9. The glueball spectrum from an anisotropic lattice study Colin Morningstar, Mike Peardon Phys. Rev. D60 (1999) 034509 Central Production in DPE at RHIC Glueball production at in DPE process at RHIC is complementary to GLUEX and PANDA Sparse spectrum! New I=0 mesons starting with 0++ 1.6 GeV 0-+ , 2++ 2.3 - 2.5 GeV No JPC-exoticglueballs until 2+- 4 GeV TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  10. f1(1285) dPT > 0.5 GeV. Strong qq f1(1285), weak G? f0(1500) 0.2 GeV < dPT < 0.5 GeV. F.E.Close and A.Kirk, PLB397, 333 (1997). f0(1500) dPT < 0.2 GeV. Very weak qq f1(1285), stronger G? f0(1500) WA102 F(1500) p+p-p+p- TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  11. BRAHMS & PP2PP (p) RHIC pC Polarimeters Absolute Polarimeter (H jet) PHENIX (p) STAR (p) e = ~10  mm mrad with scraping Siberian Snakes Spin Rotators Partial Siberian Snake Pol. Proton Source 500 mA, 300 ms Strong AGS Snake 2  1011 Pol. Protons / Bunch e = 20 p mm mrad LINAC BOOSTER AGS 200 MeV Polarimeter AGS Internal Polarimeter Rf Dipoles AGS pC Polarimeters Polarized Proton Collisions in RHIC TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  12. PP2PP Setup - tag forward protons Phys. Lett. B 579 (2004) 245-250 Phys. Lett. B 632 (2006) 167-172 Phys. Lett. B 647 (2007) 98-103 NIM A535 (2004) 415 - 420 The pp2pp Roman pots mounted on the outgoing beams, down stream from the STAR detector as shown. To achieve full azimuthal coverage for elastic events, at each location one Roman Pot station is horizontal and one vertical. RHIC accelerator magnets are used for momentum analysis resulting in forward proton taggers installed in the warm straight section between Q3 and Q4 magnets. The pp2pp Roman Pots are a moveable detector system allowing approach to the beam as closely as possible, thus extending the t and x ranges to the lowest values. TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  13. Roman Pot Stations at RHIC Roman Pot above the beam to IR Roman Pot below the beam TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  14. For MX = 2 GeV,  = 0.01 Reconstruction of the Proton Momentum Loss  Need to measure vector at the detection point, hence two RPs are needed on each side of STAR. For a proton, which scatters with  and  we have:  Accelerator transport Because  and  are small special focusing is needed TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  15. TPC: -1.0 <  < 1.0 FTPC: 2.8 <  < 3.8 FPD: ||  3.8 (p+p) ||  4.0 (p+p, d+Au) STAR STAR Detector - measure recoil system Mx TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  16. Resonance Signal in p+p and Au+Au collisions from STAR p+p  p+p Au+Au (1385) K(892) Au+Au p+p D++ p+p (1020) p+p (1520) Au+Au Au+Au TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  17. Charged hadron pT distributions measured up to 12 GeV in Au+Au, d+Au and p+p reference Leading particle spectra TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  18. Run 2008 - Phase I Projections Need to reach small t and  values to measure small masses of interest  large *=20m, special optics and beam scraping are needed. Hence a dedicated three-day run is planned • Elastic scattering: • 100% acceptance for elastic scattering for 0.003 < |t| < 0.024; • 20×106 elastic events: Db=0.31 (GeV/c)-2, Dr=0.01, Dstot = 2-3 mb; • In four t subintervals we shall have 5×106 events in each resulting in corresponding errors dAn=0.0017, dAnn=dAss=0.003. DPE process: Luminosity few ×1029 cm-2sec-1: • 4.5105 DPE events with full proton momentum reconstruction; • (5-7)106 DPE events with tagged protons - good size data sample for this physics. TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  19. A new QCD exploration at RHIC In summary the physics program with tagged forward protons at STAR will: • Study elastic scattering and its spin dependence in unexplored t and s range; • Study the structure of color singlet exchange in the non-perturbative regime of QCD; • Search for diffractive production of light and massive systems in double Pomeron exchange process; • Search for new physics, including glueballs and Odderon. The proposed studies will add to the world body of knowledge concerning QCD in the non-perturbative regime where calculations are not easy and one has to be guided by measurements. In this way the proposed program extends the physics reach of both STAR and RHIC. TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  20. The not-too-distant RHIC future? Beyond presently planned STAR / PHENIX Upgrades TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  21. A Fundamental Test of Universality:Transverse Spin Drell Yan at RHIC vsSivers Asymmetry in Deep Inelastic Scattering • Important test at RHIC of recent fundamental QCD predictions for the Sivers effect, demonstrating… attractive vs repulsive color charge forces • Possible access to quark orbital angular momentum • Latest development from DIS, first direct evidences of Sivers and Collins effects (recent new results at DIS 2007 in Műnchen, April 2007, HERMES, Diefenthaler et al.) • Requires very high luminosity (RHIC II) • Both STAR and PHENIX can make important, exciting, measurements • Discussion available at http://spin.riken.bnl.gov/rsc/ TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  22. TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  23. TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  24. Attractive vs Repulsive Sivers Effects Unique Prediction of Gauge Theory ! Simple QED example: Drell-Yan: repulsive DIS: attractive Same inQCD: As a result: TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  25. TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  26. Experiment SIDIS vs Drell Yan: Sivers|DIS= − Sivers|DY *** Probes QCD attraction and QCD repulsion *** HERMES Sivers Results RHIC II Drell Yan Projections 0 Sivers Amplitude Markus Diefenthaler DIS Workshop Munich, April 2007 0 0.1 0.2 0.3 x TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  27. Luminosity Projection to 2016 (Collider Accelerator Department) TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  28. The more distant (but still foreseeable) RHIC future? TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  29. ElectronCooling Snake IR IR Snake Candidate EIC designs eRHIC 250 GeV protons, 100 GeV/n ions ELIC (JLab) 225 GeV protons, 100 GeV/n ions 9 GeV electrons, positrons Peak lumi (e+p) ~1035 cm-2s-1 10(20) GeV electrons Peak lumi (e+p) = 2.6x1033 cm-2s-1 10 GeV electrons+positrons Peak lumi (e+p) = 0.47x1033 cm-2s-1 TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  30. How do we understand the visible matter in our universe in terms of the fundamental quarks and gluons of QCD? Explore the new QCD frontier: strong color fields in nuclei - How do the gluons contribute to the structure of the nucleon / nucleus? - What are the properties of high density gluon matter? - How do fast quarks or gluons interact as they traverse nuclear matter? Precisely image the sea-quarks and gluons in the nucleon - How do the gluons and sea-quarks contribute to the spin structure of the nucleon? - What is the spatial distribution of the gluons and sea quarks in the nucleon? - How do hadronic final-states form in QCD? TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  31. The e-A physics EIC physics agenda Broad theme: precision studies of emergent features of QCD What are the momentum distributions of quarks, anti-quarks and gluons in the nucleon? How are the symmetries of QCD manifest or broken in the nucleon? How are quarks and gluons distributed spatially in the nucleon? What is the nature of glue at high density? • How do strong fields appear in hadronic or nuclear wave functions at high energies? • What are the appropriate degrees of freedom? • How do they respond to external probes or scattering? • Is this response universal (ep, pp, eA, pA, AA)? TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  32. Kinematic reach of eRHIC and ELIC for e-A studies Region of gluon saturation TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  33. one of the first EIC measurements nDS, EKS, FGS: pQCD models with different amounts of shadowing eRHIC physics example: F2(x,Q2)(sea quarks generated by glue) EIC can distinguish pQCD and saturation model expectations TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  34. 50% of momentum carried by gluons, but still a lot we don’t know Longitudinal Structure Function FL includes systematic uncertainties TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  35. Precisely image the sea quarks Spin-Flavor Decomposition of the Light Quark Sea u u u > u d Many models predict Du > 0, Dd < 0 | p = + + + … u u u u d d d d RHIC-Spin region TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  36. GPDs and Transverse Gluon Imaging Deep exclusive measurements in ep / eA with an EIC: diffractive: transverse gluon imaging J/y, ro, g (DVCS) non-diffractive: quark spin/flavor structure p, K, r+, … [ or J/y, f, r0 p, K, r+, … ] Are gluons uniformly distributed in nuclear matter or are there small clumps of glue? Describe correlation of longitudinal momentum and transverse position of quarks/gluons  Transverse quark/gluon imaging of nucleon (“tomography”) TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  37. 2007 2010 2015 2020 RHIC II physics runs RHIC physics runs Detector Upgrades: $35M eRHIC physics runs EBIS: $20M RHIC II: $95M [FY07$] CD0 e-cooling of ion beams eRHIC: ~$700M [FY07$] CD0 e beam + new detector LHC QCD Collider Laboratory Legend: R&D Construction Multiple small projects CD0: DOE Critical Decision, mission need Long Term Strategic View TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

  38. Summary • Saturation, Low-x, and QCD are a vibrant, integral component of the ongoing and future RHIC physics program • Lots of new data just around the bend (in the next 1-2 years) • Lots of potential for major discoveries, now and in the future. TJH: Saturation, Low-x, QCD Workshop Villaggio Guglielmo, July 2-18, 2007

More Related