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EMC Effect and Short-Ranged Correlations EMC effect and short-ranged correlations Gerald A. Miller University of Washington RMP with Or Hen, Eli Piasetzky, Larry Weinstein arXiv: 1611.09748 Will focus on 0.3 <x<0.7 Remarkable experimental progress Personal view of history, but mainly what I think is new I NTERNATIONAL JOURNAL OF HIGH-ENERGY PHYSICS CERNCOURIER V OLUME 53 NUMBER 4 M AY 2013 Higinbotham, Miller, WELCOME CERN Courier – digital edition Welcome to the digital edition of the May 2013 issue of CERN Courier. Hen, Rith Last July, the ATLAS and CMS collaborations announced the discovery of a new particle at the LHC with a mass of 125 GeV. They referred to it as a “Higgs-like boson” because further data were needed to pin down more of its properties. Now, the collaborations have amassed enough evidence to identify the new particle as a Higgs boson, although the question remains of whether CERN Courier 53N4(’13)24 it is precisely the Higgs boson of the Standard Model of particle physics. The Deep in the nucleus: masses of these particles were just as electroweak theory predicted, based on a puzzle revisited other particle interactions continue to provide puzzles in more complex heavy-ion collisions. To sign up to the new issue alert, please visit: http://cerncourier.com/cws/sign-up. To subscribe to the magazine, the e-mail new-issue alert, please visit: http://cerncourier.com/cws/how-to-subscribe. HEAVY IONS ASTROWATCH IT’S A The key to fi nding Planck reveals an out if a collision almost perfect HIGGS BOSON EDITOR: CHRISTINE SUTTON, CERN is head on universe The new particle DIGITAL EDITION CREATED BY JESSE KARJALAINEN/IOP PUBLISHING, UK p31 p12 is identifi ed p21 1 CERNCOURIER WWW. V OLUME 53 NUMBER 4 M AY 2013 Eur. Phys. J. A (2016) 52: 268 Page 57 of 100 Table 5. Key measurements in e +AcollisionsatanEICtoexplorethedynamicsofquarksandgluonsina nucleusinthe non-saturation regime. Deliverables Observables What we learn 2 Collective Ratios R2 Q evolution: onset of DGLAP violation, beyond DGLAP nuclear effects from inclusive DIS A-dependence of shadowing and antishadowing at intermediate x Initial conditions for small-x evolution Transport Production of light Color neutralization: mass dependence of hadronization coefficients in and heavy hadrons, Multiple scattering and mass dependence of energy loss The EMC EFFECTnuclear matter and jets in SIDIS Medium effect of heavy quarkonium production 3 2 2 Nuclear density Hadron production Transverse momentum broadening of produced hadrons JLab Q =3-6 GeV 2 1.2 Because these data are at somewhat lower Q than D and its fluctuation in SIDIS Azimuthal φ-modulation of produced hadrons σ 2 2 / E03103 Norm. (1.6%) previous high-x results, typically Q =5 or 10 GeV for C SLAC E139 [2], extensive measurements were made to σ 1.1 SLAC Norm. (1.2%) verify that our result is independent of Q2.Thestruc- ture functions were extracted at several Q2 values and 1.2 fort to study the properties of quarks and gluons and their found to be consistent with scaling violations expected 1 EMC E136 from QCD down to Q2 ≈ 3GeV2 for W 2 ≥ 1.5GeV2, 1.1 dynamics in the nuclear environment both experimentally while the structure functions ratios show no Q2 depen- NMC E665 and theoretically. dence. Figure 1 shows the carbon to deuteron ratio for 0.9 2 2 1 Using the same very successful QCD formulation at the five highest Q settings (the lowest and middle Q 1.2 D D 2 values were measured with a 5 GeV beam energy). There σ / E03103 Norm. (1.7%) the leading power in Q for proton scattering, and using 2 / F is no systematic Q dependence in the EMC ratios, even Be 0.9 σ 1.1 SLAC Norm. (1.2%) Ca the DGLAP evolution for the scale dependence of par- at the largest x values, consistent with the observation 2 of previous measurements [3]. F 0.8 ton momentum distributions, several QCD global analy- 1 ses have been able to fit the observed non-trivial nuclear 1.2 D Q2=4.06 0.7 σ / dependence of existing data, attributing all observed nu- 2 C Q =4.50 σ 2 0.9 clear dependences —including its x-dependence and nu- Q =4.83 0.6 EIC 1.1 2 Q =5.33 1.2 D clear atomic weight A-dependence— to a set of nucleus- 2 Q =6.05 σ / E03103 Norm. (1.5%) 0.5 dependent quark and gluon distributions at an input scale 4He 0.0001 0.001 0.01 0.1 1 1 σ 1.1 SLAC Norm. (2.4%) Q0 ! 1GeV[176,178,179].Asanexample,thefittingre- x sult of Eskola et al. is plotted along with the data on the 1 0.9 Fig. 56. The ratio of nuclear over nucleon F2 structure func- ratio of the F2 structure function of calcium divided by tion, R2, as a function of Bjorken x,withdatafromexisting that of deuterium in fig. 56, where the dark blue band 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 0.9 fixed target DIS experimentsWhite at Q2 > 1GeVPaper2,alongwiththe indicates the uncertainty of the EPS09 fit [176]. The suc- x 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 QCD global fit from EPS09 [176]. Also shown is the expected cess of the QCD global analyses clearly indicates that the kinematic coverage of the inclusive measurements at the EIC. FIG. 1: (Color online) Carbon EMC ratios [10] for the five x response of the nuclear cross-section to the variation of highest Q2 settings (Q2 quoted at x =0.75). Uncertainties The purple error band is the expected systematic uncertainty 12 9 4 the probing momentum scale Q Q0 is insensitive to the are the combined statistical and point-to-point systematic. ForFIG. 2: (Color 0.3<x<0.7 online) EMC ratios for ratio=RC, Be, and He [10], is approximately linear ! 9 at the EIC assuming a 2% (a total of 4%) systematic er- The solid curve is the SLAC fit [2] to the Carbon EMC ratio. compared to SLAC [2]. The Be results include a correc- ± nuclear structure, since the DGLAP evolution itself does Nucleontion for the neutron structure excess (see text). Closed is modified: (open) circles ror, valence while the statistical quark uncertainty momentum is expected depleted. to be much 2 2 not introduce any nuclear dependence. However, it does For all further results, we show the ratios obtained denote W above (below) 2 GeV .Thesolidcurveisthe smaller. ◦ A-dependent fit to the SLAC data, while the dashed curve Why are ratios independent from the 40 data (filled squares in Fig. 1). While there 12 not answer the fundamental questions: Why are the par- ◦ is the fit to C. Normalization uncertainties are shown in 2 are data at 50 (open circles) for all nuclei, the statis- EFFECTSparentheses for both measurements. ARE SMALL ~15% 2 ton distributions in a nucleus so different from those in a tical precision is noticeably worse, and there are much of Q ? larger corrections for charge symmetric background and free nucleon at the probing scale Q0?Howdothenuclear Coulomb distortion (for heavier nuclei). high-energy proton collisions with a momentum transfer structure and QCD dynamics determine the distributions The EMC ratios for 12C, 9Be, and 4He are shown in data from HERMES. Note that the HERMES 3He data larger than 2 GeV (corresponding to hard scatterings tak- of quarks and gluons in a nucleus? Fig. 2 along with results from previous SLAC extractions. have been renormalized by a factor of 1.009 based on ing place at a distance less than one tenth of a femtome- The 4He and 12Cresultsareingoodagreementwiththe comparisons of their 14NEMCeffect and the NMC 12C The nucleus is a “molecule” in QCD, made of nucleons SLAC results, with much better precision for 4He in the result [11]. We show both the measured cross section ter). —which, in turn, are bound states of quarks and gluons. new results. While the agreement for 9Be does not ap- ratio (squares) and the “isoscalar” ratio (circles), where pear to be as good, the two data sets are in excellent the 3He result is corrected for the proton excess. Previ- Are the quarks and gluons in a nucleus confined within Unlike the molecule in QED, nucleons in the nucleus are agreement if we use the same isoscalar correction as E139 ous high-x EMC measurements used a correction based the individual nucleons? Or does the nuclear environment packed next to each other, and there are many soft gluons (see below) and take into account the normalization un- on an extraction of the F2n/F2p ratio for free nucleons 2 significantly affect their distributions? The EMC experi- inside nucleons when probed at small x.TheDISprobe certainties in the two data sets. In all cases, the new data from high Q measurements of F2d/F2p.Weuseglobal extend to higher x,althoughatlowerW 2 values than the fits [12, 13] to the free proton and neutron cross sections ment at CERN [213] and experiments in the following two has a high resolution in transverse size 1/Q.Butits SLAC ratios. The EMC ratio for 4He is comparable to evaluated at the kinematics of our measurement and then decades clearly revealed that the momentum distribution resolution in the longitudinal direction, which∼ is propor- 12C, suggesting that the modification is dependent on the broadened using the convolution procedure of Ref. [14] to average nuclear density, which is similar for 4He and 12C, yield the neutron-to-proton cross section ratio in nuclei.
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