The EMC Effect Cannot Be Explained by Conventional Nuclear Physics

Nucleons in the Nuclear Environment "The next seven years..." John Arrington Argonne National Lab

Topic: Study of nucleons (hadrons, quarks) in nuclei 1 - The EMC effect and related measurements [S. Kuhn, S. Strauch, J. Watson] 2 - Color Transparency [D. Dutta] 3 - Quark propagation [W. Brooks] 4 - J/ψ production [P. Bosted]

Jefferson Lab User's Group Annual Meeting, June 18, 2004 "Beam in 30 minutes or it's free" Nucleons in the Nuclear Environment "The next seven years..." John Arrington Argonne National Lab Bigger question: Does QCD matter in the real world? In the lab (GeV accelerators), matter is quarks In the real world, matter is hadrons

Questions for JLab: How do nucleons interact with the nucleus? How do other (exotic?) hadrons interact with the nucleus? How do quarks interact with the nucleus?

Jefferson Lab User's Group Annual Meeting, June 18, 2004 "Beam in 30 minutes or it's free" Two "Realms" of Nuclear Physics QCD land quarks + gluons + color V(r) 2.0 [GeV] 1.6 Strongly attractive at all distances: 1.2 1 GeV/cm = 18 tons! 0.8 >1012 times the coulomb 0.4 0 attraction in hydrogen potential between -0.4 two quarks -0.8 Real world 0.5 1.0 1.5 2.0 2.5 nucleons + mesons + strong interaction r [fm]

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 Don't observe quarks, gluons, or color in traditional nuclear physics r [fm] ~1 fm Quarks have been swept under a very heavy (18 ton) rug When do quarks matter? To peek under the rug, we have to shift the 18 ton weight at least a little bit

High energy early universe LHC Cosmic rays quark-gluon SLAC, DESY, LHC... RHIC plasma

The The 250 Titanic Iceberg 200 SPS High temperatures chemical freeze-out temperature T (MeV) 150 Early universe AGS deconfinement RHIC? 100 chiral restoration thermal freeze-out SIS High densities 50 hadron gas atomic Neutron stars nuclei neutron stars

Nuclei?? 0.3 1 2 5 8 JLab???? NET BARYON DENSITY (0.17 GeV/fm3) JLAB12

We do see density-dependent effects in nuclear structure (EMC effect) Do these effects have anything to do with the quarks?

CERN ≅ shifting an 18 ton weight by dropping the titanic on top of it (titanic=13550 tons=700 GeV, (some sites, 20-40ktons) iceberg=150k-300k tonnes (8-16 TeV), SLAC=50GeV=900 Tons). SUV=2-3 (some 4) tons. 747=435 tons. Medium modifications to nucleon structure?

Depletion of the structure EMC effect for Iron (Copper) function for 0.3

The magnitude of the effect increases with size/density

The x-dependence is identical for all nuclei

It has been clear for some time that binding, Fermi motion play important roles. Do we need something more than conventional nuclear physics?

Recently shown that... The EMC effect cannot be explained by conventional nuclear physics... most recently - J. Smith and G. A. Miller, PRC 65:015211 (2002)

Unless it can be explained by conventional nuclear physics. most recently - J. Rozynek and G. Wilk, NPA 721, 388 (2003) The CoulombSumRuleis fulfilled... Unless itcanbeexplained by conventionalnuclearphysics The EMCeffectcannotbeexplainedbyconventional nuclearphysics... scattering +nucleondistributionin nucleus nothing morethannucleonelastic Quasielastic responseis(basically) What elsedoweknowaboutmediummodifications? J. Carlsonetal.,PLB553,191(2003) J. Jourdan,NPA603,117(1996) most recently-J.RozynekandG.Wilk,NPA 721,388(2003) most recently-J.SmithandG.A.Miller,PRC65:015211(2002) arXiv:nucl-th/0208039 v1 21 Aug 2002 What else do we know about medium modifications? The EMC effect cannot be explained by conventional nuclear physics... most recently - J. Smith and G. A. Miller, PRC 65:015211 (2002) Unless it can be explained by conventional nuclear physics most recently - J. Rozynek and G. Wilk, NPA 721, 388 (2003)

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The Coulomb Sum Rule is fulfilled... 3 1.1 He 40 a) J. Jourdan, NPA 603, 117 (1996) Ca 1.0 48 Ca J. Carlson et al., PLB 553, 191 (2003) 56 0.9 Fe ) 208

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Except that maybe it isn't.

L 0.7 J. Morgenstern, Z.-E. Meziani, PLB 515, 269 (2001) S 0.6 0.5

Integrated quasielastic response 3 1.1 He 40 b) suppressed by ~30-40% Ca 1.0 56 Fe 208 0.9 Pb 56 0.8 Fe 56 0.7 Fe 0.6 0.5 0.4 200 300 400 500 600 1100 1200

qeff (MeV/c) What else do we know about medium modifications? The EMC effect cannot be explained by conventional nuclear physics... most recently - J. Smith and G. A. Miller, PRC 65:015211 (2002) Unless it can be explained by conventional nuclear physics most recently - J. Rozynek and G. Wilk, NPA 721, 388 (2003)

The Coulomb Sum Rule is fulfilled... J. Jourdan, NPA 603, 117 (1996) J. Calrson et al., PLB 553, 191 (2003) Except that maybe it isn't. J. Morgenstern, Z.-E. Meziani, PLB 515, 269 (2001)

Nucleon form factors are modified in nuclei... G. Van der Steenhoven, et al., PRL 57, 182 (1986) [form factor ratio in nuclei]

GE/GM modified for nucleons in a nucleus What else do we know about medium modifications? The EMC effect cannot be explained by conventional nuclear physics... most recently - J. Smith and G. A. Miller, PRC 65:015211 (2002) Unless it can be explained by conventional nuclear physics most recently - J. Rozynek and G. Wilk, NPA 721, 388 (2003)

The Coulomb Sum Rule is fulfilled... J. Jourdan, NPA 603, 117 (1996) J. Carlson et al., PLB 553, 191 (2003) Except that maybe it isn't. J. Morgenstern, Z.-E. Meziani, PLB 515, 269 (2001) DEAD Nucleon form factors are modified in nuclei... END? G. Van der Steenhoven, et al., PRL 57, 182 (1986) [form factor ratio in nuclei] Unless they aren't. T. D. Cohen, J.W. Van Orden, A. Picklesimer, PRL 59, 1267 (1987) [form factor ratio in nuclei] I. Sick, NPA 434, 677 (1985) R.W. McKeown, PRL 56, 1452 (1986) [y-scaling limits] What do we really know about medium modifications? The EMC effect cannot be explained by conventional nuclear physics... most recently - J. Smith and G. A. Miller, PRC 65:015211 (2002) Unless it can be explained by conventional nuclear physics most recently - J. Rozynek and G. Wilk, NPA 721, 388 (2003)

The Coulomb Sum Rule Theis fulfilled... effects are small J. Jourdan, NPA 603, 117 (1996) J. Carlson et al., PLB 553, 191 (2003) Except that maybe it isn't. J. Morgenstern, Z.-E. Meziani, PLB 515, 269 (2001)

Nucleon form factorsThe are modified experiments in nuclei... are hard G. Van der Steenhoven, et al., PRL 57, 182 (1986) [form factor ratio in nuclei] Unless they aren't. T. D. Cohen, J.W. Van Orden, A. Picklesimer, PRL 59, 1267 (1987) [form factor ratio in nuclei] I. Sick, NPA 434,The 677 (1985) theory is very complicated R.W. McKeown, PRL 56, 1452 (1986) [y-scaling limits]

Jefferson Lab needs to do more than just improve a few measurements... What can Jefferson Lab do?

1) Improve a few measurements (better facility) EMC effect Coulomb sum rule y-scaling limits on nucleon `swelling'

2) Make new measurements (better techniques) Form factor modification by polarization transfer

3) Invent new techniques (brand new ideas) Measure EMC effect as a function of local density Probe high-density components of nucleus (SRCs) EMC effect in the resonance region E89-008 (4 GeV) - 1.2 < W2 < 3.0 Q2 ≅ 4 GeV2

Identical nuclear dependence in DIS and resonance regimes! EMC effect - purely hadronic? Consequence of precise duality?

Relaxing the DIS limit appears to yield identical results, with improved precision at large x Indication of different shape for Carbon at large x

Any deviation from the DIS result should be even smaller at 6 GeV EMC effect in very light nuclei <ρ F2(A)/F2(D) - Vary with A or A> ? x-dependence same for all nuclei? New measurements planned for 3He and 4He: Provide more information on the A-dependence Allow comparison to models in exact few-body calculations The shape in 3He, 4He will provide a new way to test the existing models

SLAC fit to heavy nuclei (scaled to 3He) Calculations by Pandharipande and Benhar for 3He and 4He

E01-001, Hall C, September 2004 σ σ Extending EMC effect measurements to F2 and R= L/ T

Preliminary

RA/RD from HERMES Rp from JLab [E99-118] [also E94-110, E00-002]

Additional experiments approved to measure RD [E02-109] and RA [E04-001]

Are nuclear effects identical in FL and F2 ? 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 E03-104 approved by PAC24 to make additional, high precision measurements [S. Strauch - Details on the physics, experiment, models] Crazy New ideas: 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 thermal freeze-out SIS Average nuclear density is

50 a few times smaller than hadron gas atomic nuclei neutron stars the critical density

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! 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 Nucleon separation is limited by nuclear density the short range repulsive core

V(r) Potential between two nucleons 1.2 fm separation

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~1 fm r [fm]

For a 1 fm separation (typical for SRCs), 0.6 fm separation the central density is ~4x nuclear matter. >5 times Comparable to neutron star densities! nuclear matter densities Warning: portions of the person seated next to you are at neutron star densities and may collapse without warning

With no degeneracy to keep you from collapsing in upon yourself at any moment The person sitting next to you could collapse at any moment, without warning! Frankfurt and Strikman Frankfurt, Day, Sargsian, Iron MF+multi-nucleon MF+2N Mean field and Strikman

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Inclusive x>1 --> isolate SRC

Inclusive DIS --> quark PDFs Red curve: 2H = p + n JLab 12 GeV --> DIS scattering at x>1 Blue curve: 2H = 0.95(p+n) + 0.05(6q) --> PDF for SRC F2(x) Expect any `quark-mixing' between nucleons to increase strength at large x

Deuteron provides cleanest signature Inelastic dominated (we understand deuteron as p+n) for JLab 12 kinematics Heavy nuclei may yield larger signals, but need better understanding of SRCs for hadronic `baseline'

SRCs provide a high-density component in nuclei Important to understand their impact on nuclear structure More than just as a baseline when looking for `exotic' effects

Need data on light nuclei to allow separation of nuclear effects from 2N, 3N correlations. Completed measurements:SLAC, JLabHallsB,C multi-nucleon correlations add E02-019 willexpandkinematic range, Sensitive tosizeofSRCs Very largekinematicrange Sensitive to2-Nvs.multi-nucleon SRCs Sensitive tonucleonmomentumdistribution Inclusive A(e,e')atlargex 3 Q Scaling region He and 2 >3GeV 4 He tobetter study2Nvs. 2 Studies ofShort-RangeCorrelations SLAC E89-008 E02-019 (Sep2004) nuclei at high Q E01-015 willmeasure A(e,e'NN)for heavier E00-102 extended A(e,e'p) atlargeP 100 cross section (fb/(MeV/c) ) cross section (fb/(MeV/c) ) Completed measurements:JLabHalls A,B,C 10 20 30 50 Sensitive todetailsofSRCs More limitedkinematicrange Sensitive to2-Nvs.multi-nucleon SRCs Sensitive tothefullspectralfunction 0 0 0 c) a) 0.2 P [Details -J. Watson] rel (GeV/c) 0.4 0.6 2 16 pp pn O(e,e'p) measurements m 0 andA(e,e'NN) d) b) 0.2 P tot Hall B, (GeV/c) breakup 0.4 PWIA Full 1 Body Data 0.6 5 3 He pp pn 0.8 Probing SRCs, part 2: Tagged EMC effect

1.05 x=0.3 Strike neutron in 1 2 0.4 ~EMC H, tag proton effect for 0.95 0.5 x=0.6 Carbon θ≅ o n Proton at 180 --> spectator R 0.9 (reconstruct initial nucleon) 0.85 Proton at low momentum --> R = Fbound / Ffree suppress FSI, off-shell effects n 2 2 0.8 0 100 200 300 400 Small P --> ~free neutron S |p| (MeV/c) Large PS --> Isolate SRCs For low spectator momentum, R ≅ 1 (high-density configuration) Nuclear effects much larger for high-momentum spectators Spectator proton acts as a `knob' we can use to vary EMC effect: structure of a nucleus as a the density of the pair function of average nuclear density Tagged EMC effect: structure of a SRC as a function of local density Preliminary results (high spectator momentum - high density) in <40 minutes [S. Kuhn] E03-012: BoNuS (low spectator momentum - free neutron) 2005 Nucleons in High Density Matter: the EMC effect and beyond Improved experiments of the EMC effect Improved precision for EMC effect at large x EMC effect in few-body nuclei (better calculations, different shape) Better measurements of Coulomb sum rule Better limits on nucleon `swelling' New experiments, not possible before JLab

EMC effect for both F2 and R Nucleon form factors inside of a nucleus Hall B: use CLAS to tag high-p spectators independent low-p tagger (BONUS) New ways to measure nucleon modification Probe internal structure of high density configuration Tag high-momentum spectator to isolate high density SRCs, low-momentum spectator to isolate almost free nucleons Measure distribution of superfast quarks (DIS at x>1) This is not your father's Oldsmobile EMC effect "Nucleons in the Nuclear Environment"

Why stop with nucleons? We can put other stuff in nuclei

How do other (exotic?) hadrons interact with the nucleus? Point-like configurations - Color Transparency Intrinsically small hadrons - sub-threshold J/ψ production

How do quarks interact with the nucleus? Quark propagation, quark hadronization in a hadronic medium

Examine QCD in other `extreme' cases Look for QCD (color) degrees of freedom in nuclei Color Transparency pQCD predicts that a hadron in a point-like configuration (PLC) will have a very small color interaction due to the cancellation of the color charge

Standard example: Proton knockout reaction -Form PLC in hard, exclusive interaction [requires high-Q2. How high?] -PLC travels through nucleus [requires PLC to `survive' ~1 fm or more]

-PLC has reduced interaction with nucleus --> reduced absorption 2 [extract transparency = σA / σH as function of Q ]

A well designed set of experiments can study the formation, evolution, and interaction of this exotic QCD state Color Transparency: Mesons vs. Baryons CT in a qqq system: -No analogous state in QED CT in a qq system: -Analogous to small electric dipole -Two quarks --> expect easier formation of PLC expect slower evolution back to normal size

Transparency vs. Q2: Vary PLC formation, lifetime, Color Transparency Transparency vs. A: Study Lifetime (evolution) of the PLC CT in mesons vs. baryons: Separate CT from PLC formation/lifetime

So far, no unambiguous evidence for CT in baryons Limited evidence in meson (π, ρ) attenuation [HERMES, JLab] Signal in jet production at FNAL Indicates full CT by Q2 ≅ 10 GeV2 Different mechanism for PLC formation then in knockout reactions [More details - D. Dutta] Color Transparency: Rescattering vs. attenuation

Without rescattering, A(e,e'p) maps out spectral function

Rescattering dominates for large Pm

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0 --> Larger signal 0 2 4 6 8 10 12 14 16 18 20 Q2 (GeV2) --> Insensitive to PLC evolution beyond ~1 fm Large kinematic range at 12 GeV, already have some results from Hall B [K. Egiyan - thurs. morning] Color Transparency in meson rescattering

Meson --> PLC formation is easier 0.11 D(e,e'ρ) Rescattering --> ~independent of 0.1 PLC evolution

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By combining different measurements... we can disentangle the relevant effects Meson vs. Baryon PLC formation Knockout vs. Rescattering PLC evolution Q2- and A-dependence Reduced color interaction Quark propagation through Nuclei

Inclusive DIS measurements are "fire and forget" High energy virtual photon hits "free" quark --> scaling, quark distribution functions, etc... The "free" quark disappears into the ether after it is struck

We create and then discard a tagged quark beam inside of a target nucleus by requiring that the reaction be a QCD-free zone Inclusive scattering from partons is clean and simple, QCD is not

We could use this ``beam'' to study... Quark interaction (energy loss, rescattering) with high-density hadronic matter Effect of the nuclear medium on quark hadronization

If DOE offered us an accelerator with these parameters, we would be crazy to pass it up, even if it takes some hard work to interpret all of the measurements! HERMES has made such measurements, but with relatively low luminosity, and (for the first few years) mostly for the proton and deuteron E02-104 (Hall B, spring 2004): Measured production of π0, π+/-, K+/-, p from deuterium, carbon, iron, tin, lead as a function of ν, q, z, pT to study attenuation, hadronization, and transverse momentum broadening Quark propagation through Nuclei

HERMES has made such measurements, but with relatively low luminosity, and (for the first few years) mostly for the proton and deuteron E02-104 (Hall B, spring 2004): Measured production of π0, π+/-, K+/-, p 6 hadrons from deuterium, carbon, iron, tin, lead x 5 targets as a function of ν, q, z, pT x 4 variables to study attenuation, hadronization, x 3 topics and transverse momentum broadening [360 details - W. Brooks]

E02-104: A dedicated, high-luminosity study of quark propagation at 5 GeV

12 GeV upgrade Larger kinematic range Expect factorization to be a better Simpler interpretation approximation at higher energy J/ψ production

Intrinsically small size c-c pair Unusual bound state of QCD Probe of color Small size --> weaker interaction interaction color Van der Waals interaction

Virtually no charm quarks in nucleons Quark exchange suppressed Probe of exotic color 2-gluon exchange dominates - sensitive to short configurations in nuclei range effects (e.g.hidden color)

Little is known about it's interactions J/ψ suppression an important signature for QGP formation J/ψ propagation in cold hadronic matter well known

Exotic effects have been observed at charm threshold Possible source of apparent 'CT' signature in Brookhaven (p,2p) data? Large asymmetry in double-polarized proton-proton scattering

[Details - P. Bosted] J/ψ production in Nuclei

Small size --> weaker interaction color Van der Waals interaction E03-008(Hall C):Measure J/ψ production for various nuclei Attenuation --> ψ-N cross section ¦ ¦ £ £ ¡

Unusual reaction mechanism --> sensitive to small components of nuclear structure

Observe in sub-threshold production from SRC γ ψ Probe 'hidden color' in nucleus Is having every nucleon be in a color singlet state the only way for a nucleus

to be in a color singlet state? Does QCD matter in the "real world"?

early universe Experiments in nuclei open up LHC quark-gluon unique new windows on QCD RHIC plasma in nuclei (nuclear structure): 250

- Quark degrees of freedom 200 SPS in matter at high density chemical freeze-out temperature T (MeV) 150 AGS - Color degrees of freedom in deconfinement 100 chiral restoration nuclei (hidden color) thermal freeze-out SIS 50 hadron gas atomic nuclei neutron stars Program is not limited to 0.3 1 2 5 8 learning about the "real world": NET BARYON DENSITY (0.17 GeV/fm 3) JLAB12 - Provide detailed information on the EMC effect, nucleon modification in nuclei, Color Transparency, quark energy loss, J/ψ production and interaction, etc... - In the end, these all tell us something about QCD

Finally, this physics has applications to other areas of fundamental research: - Complements RHIC/LHC studies of QCD at high temperature - ν-oscillation and scattering measurements: need form factors, structure function, models of nuclear effects to interpret results - J/ψ production and attenuation are input to QGP searches - Cold, dense matter important for neutron stars/astrophysics