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Superfast Quarks, Short Range Correlations and QCD at High Density John Arrington Argonne National Laboratory

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Superfast Quarks, Short Range Correlations and QCD at High Density John Arrington Argonne National Laboratory Superfast Quarks, Short Range Correlations and QCD at High Density John Arrington Argonne National Laboratory A(e,e’) at PDFs at x>1 High Energy Superfast quarks PN12, The Physics of Nuclei with 12 GeV Electrons Workshop, Nov. 1, 2004 Superfast Quarks, Short Range Correlations and QCD at High Density John Arrington Argonne National Laboratory Nuclear structure SRCs Nuclear PDFs A(e,e’) at PDFs at x>1 EMC effect High Energy Superfast quarks QCD Phase Transition Cold, dense nuclear matter PN12, The Physics of Nuclei with 12 GeV Electrons Workshop, Nov. 1, 2004 Short Range Correlations (SRCs) Mean field contributions: k < kF Well understood High momentum tails: k > kF Calculable for few-body nuclei, nuclear matter. Dominated by two-nucleon short range correlations. Calculation of proton momentum distribution in 4He Wiringa, PRC 43 k > 250 MeV/c 1585 (1991) 15% of nucleons 60% of the K.E. k < 250 MeV/c 85% of nucleons 40% of the K.E. Isolate short range interaction (and SRCs) by probing at high Pm (x>1) V(r) N-N potential Poorly understood part of nuclear structure Significant fraction of nucleons have k > kF 0 Uncertainty in short-range interaction leads to uncertainty at large momenta (>400-600 MeV/c), even for the Deuteron r [fm] ~1 fm A(e,e’): Short range correlations 56Fe(e,e/ )X We want to be able to isolate and probe -1 10 /A 2 Fe two-nucleon and multi-nucleon SRCs F -2 F2 /A 10 x=1 x = 1 -3 10 -4 Dotted =mean field approx. 10 -5 10 Solid = +2N SRCs. x=1.5 -6 -Frankfurt, Day, Sargsian, and 10 Strikman, Phys. Rev. C (1993) -7 10 x = 1.5 Dashed = +multi-nucleon. -8 -Frankfurt and Strikman, 10 - JLab data Phys. Lett. B94 (1980) 216 -9 (E89-008) 10 - JLab12 projected data -10 10 Inclusive scattering at x>1: 2.5 5 7.5 10 12.5 15 17.5 20 22.5 25 Q2, GeV2 4 GeV data cominated by QE scattering - consistent with 2N SRCs 6 GeV can reach Q2=11 GeV2 - more sensitive to multi-nucleon contributions JLab12 can reach Q2=23 GeV2 - even more sensitive, especially at higher x values Special cases - 3He and 3H Just as comparison of A/D is sensitive to 2N SRCs, comparison of heavy nuclei to A=3 can tell us about nature, strength of 3N SRCs A(e,e’p) and (e,e’NN) probes of 3He are already able to provide more information about the nature of SRCs. 12 GeV will yield reduced FSI, MEC contributions Comparison of 3H and 3He will tell us more about isospin-dependence of short range correlations (n-n vs. n-p vs. p-p pairs) Comparison of 3H and 3He will allow better extraction of neutron structure than deuteron measurements Mapping out Short Range Correlations (nucleonic degrees of freedom, nuclear structure) 6 GeV QE (e,e’): -Map out A-dependence of 2N SRCs -Look for signal of multi-nucleon correlations (e,e’p) and -Probe spectral function at high Em,pm - study (e,e’NN): FSIs and MECs, try to isolate spectral function 12 GeV QE (e,e’): -Larger values of x, Q2 should allow us to separate and map out multi-nucleon SRCs (e,e’p) and -Probe spectral function at high Em,pm in regions (e,e’NN): where FSIs and MECs are small or calculable -Isolate SRCs by ’tagging’ the nucleon that was not struck Goal: a complete picture of SRCs in terms of nucleonic degrees of freedom --> Improve for our understanding of nuclei --> Relevant to other areas of physics e.g. Burrows and Sawyer, PRC58:554(1998) Structure of neutron stars S. Reddy, et al., PRC59:2888(1999) Sub-threshold production measurements ν-A interactions: modeling supernovae, high-precision ν θ measurements of scattering (oscillations, 13) e.g. H. Nakamura, et al., hep-ph/0409300 Two "Realms" of Nuclear Physics QCD land V(r) 2.0 quarks + gluons + color [GeV] 1.6 Strongly attractive at all distances 1.2 0.8 1 GeV/cm = 18 tons 0.4 12 >10 times the coulomb 0 potential between attraction in hydrogen -0.4 two quarks -0.8 0.5 1.0 1.5 2.0 2.5 r [fm] Real world nucleons + mesons + strong interaction Matter consists of colorless V(r) Potential between bound states of QCD two nucleons Quark interactions cancel at large distances, making the interactions of hadrons finite 0 Nucleons appear to be fundamental objects until we probe deeply enough r [fm] to see the quark degrees of freedom ~1 fm When do quarks matter? To reveal the quarks, we need a large energy scale that can overcome the binding 2 High energy x = 0.07 Cosmic rays 1.8 x = 0.09 x = 0.10 SLAC, DESY, LHC... 1.6 x = 0.11 x = 0.14 1.4 x = 0.18 1.2 x = 0.225 x = 0.275 1 2 x = 0.35 0.8 2 DIS allows us to extract the quark F (x,Q ) + c(x) x = 0.45 0.6 x = 0.50 distributions in the nucleon x = 0.55 Test QCD (e.g. scaling, evolution) 0.4 x = 0.65 x = 0.75 Map out the non-perturbative 0.2 structure of hadrons x = 0.85 0 See the end result of confinement 1 10 100 1000 Q2 (GeV/c)2 When do quarks matter? To reveal the quarks, we need a large energy scale that can overcome the binding High energy early universe LHC Cosmic rays quark-gluon SLAC, DESY, LHC... RHIC plasma 250 High temperatures 200 SPS Early universe chemical freeze-out temperature T (MeV) 150 RHIC? AGS deconfinement 100 chiral restoration thermal freeze-out SIS 50 hadron gas atomic nuclei neutron stars 0.3 1 2 5 8 NET BARYON DENSITY (0.17 GeV/fm3) JLAB12 RHIC: Breakdown of confinement with large internal energy scale Study QCD phase transition from hadronic to quark-gluon phase Study quark-gluon matter in deconfined (?) phase When do quarks matter? To reveal the quarks, we need a large energy scale that can overcome the binding High energy early universe LHC Cosmic rays quark-gluon SLAC, DESY, LHC... RHIC plasma 250 High temperatures 200 SPS Early universe chemical freeze-out temperature T (MeV) 150 RHIC? AGS deconfinement 100 chiral restoration thermal freeze-out SIS High densities 50 hadron gas atomic Neutron (quark?) stars nuclei neutron stars Nuclei? 0.3 1 2 5 8 JLab?? NET BARYON DENSITY (0.17 GeV/fm3) JLAB12 At large enough densities, confinement should break down *Nucleons may swell or deform *Exotic structures may form (e.g. 6-quark bag) *Quarks may be fully deconfinded (quark stars?) High Density Configurations 1.7 fm separation Nucleons are already closely packed in nuclei Ave. separation ~1.7 fm in heavy nuclei nucleon charge radius ~ 0.86 fm Average nuclear Nucleon separation is limited by density the short range repulsive core V(r) Potential between two nucleons 1.2 fm separation 3x nuclear 0 matter ~1 fm r [fm] Even for a 1 fm separation, the 0.6 fm separation central density is ~4x nuclear matter. >5 times Comparable to neutron star densities! nuclear matter densities High enough to modify nucleon structure? Quark structure of nuclei: EMC effect We do see density-dependent effects in nuclear structure EMC effect for Iron (Copper) Depletion of the structure function for 0.3<x<0.8 Magnitude of the depletion increases with size/density qA(x) = qp/n(x) nA(k) It has been clear for some time that binding, Fermi motion play important roles. Do we need something more than conventional nuclear physics? JLab12: Extend traditional EMC measurements Improved data on large-x ratios and the A-dependence of the EMC effect EMC effect for separated structure functions Flavor dependence, quark vs. antiquark (Drell-Yan, ν-A DIS, Semi-inclusive DIS) Beyond "The EMC Effect" Some models, e.g. Quark-Meson Coupling model (Thomas, et al.), predict modified nucleon form factors as a consequence (or cause) of the EMC effect 15-20% 30-35% If nucleon modification explains the EMC effect, why probe nuclei? Probe nucleons! Previous attempts to look for nucleon form factor modification had mixed results - Nuclear effects large for quasielastic cross section measurements 2 - Almost no sensitivity to GE at large Q (e.g. y-scaling limits) JLab luminosity, polarization, polarimetry --> Study in-medium form factors using the polarization transfer technique Polarization transfer in 4He(e,e’p)3He E93-049 (Hall A): Compare R=GE/GM of a bound proton to GE/GM of a free proton Nuclear effects are small (dotted and dashed lines) Data are systematically ~10% below calculations without modification Indication of modified form factors in a nucleus Additional data to come... Another idea: Probe even higher densities early universe LHC quark-gluon RHIC plasma 250 200 SPS chemical freeze-out temperature T (MeV) 150 AGS deconfinement 100 chiral restoration Average nuclear density is thermal freeze-out SIS a few times smaller than 50 hadron gas atomic the critical density nuclei neutron stars 0.3 1 2 5 8 NET BARYON DENSITY (0.17 GeV/fm3) LowJLAB12 temperature high density A nucleus is a dynamic system, with local fluctuations in density These fluctuations provide a small high-density component (short-range correlations) * This may be origin of EMC effect, medium modifications * We can try to isolate SRCs to probe high density matter If SRCs are the source of the EMC effect, why probe nuclei? Probe SRCs instead! Quark distributions at x>1 With 11 GeV beam, we should be in the scaling 11 GeV ("DIS") region up to x~1.4 Inelastic dominates Existing measurements of duality in nuclei suggest we 6 GeV (E02-019) may be able to reach larger x 4 GeV (E89-008) --> Extract the distribution of ’super-fast’ quarks Two measurements (very high Q2) exist so far: ν -8x CCFR ( -C): F2(x) ~ e Limited x range, poor resolution µ -16x BCDMS ( -Fe): F2(x) ~ e Limited x range, low statistics JLab@12 GeV will allow high precision measurements for x>1 High-density configurations: quark distributions at x>1 The EMC effect compares light nuclei to heavy nuclei in order to see the effect of changing the average density (0.06-0.15 nucleons/fm-3) Probing the quark structure of SRCs allows us to see the effect of changing local density.
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