Nucleon structure functions, as measured in lepton-nucleon scattering, have historically provided a critical observable in the study of partonic dynamics within the nucleon. However, at very large parton momenta, it is both experimentally and theoretically challenging to extract parton distributions due to the probable onset of nonperturbative contributions and the unavailability of high-precision data at critical kinematics. Extraction of the neutron structure and the d quark distribution have been further challenging because of the necessity of applying nuclear corrections when utilizing scattering data from a deuteron target to extract the free neutron structure. However, a program of experiments has been carried out recently at the energy-upgraded Jefferson Lab electron accelerator aimed at significantly reducing the nuclear correction uncertainties on the d quark distribution function at large partonic momentum. This allows leveraging the vast body of deuterium data covering a large kinematic range to be utilized for d quark parton distribution function extraction. In this Letter, we present new data from experiment E12-10-002, carried out in Jefferson Lab Experimental Hall C, on the deuteron to proton cross section ratio at large Bjorken x. These results significantly improve the precision of existing data and provide a first look at the expected impact on quark distributions extracted from parton distribution function fits.

A test of lepton flavor universality in B ± → K ± μ + μ − and B ± → K ± e + e − decays, as well as a measurement of differential and integrated branching fractions of a nonresonant B ± → K ± μ + μ − decay are presented. The analysis is made possible by a dedicated data set of proton-proton collisions at s = 13 TeV recorded in 2018, by the CMS experiment at the LHC, using a special high-rate data stream designed for collecting about 10 billion unbiased b hadron decays. The ratio of the branching fractions B ( B ± → K ± μ + μ − ) to B ( B ± → K ± e + e − ) is determined from the measured double ratio R ( K ) of these decays to the respective branching fractions of the B ± → J / ψ K ± with J / ψ → μ + μ − and e + e − decays, which allow for significant cancellation of systematic uncertainties. The ratio R ( K ) is measured in the range 1.1 < q 2 < 6.0 GeV 2 , where q is the invariant mass of the lepton pair, and is found to be R ( K ) = 0.78 − 0.23 + 0.47 , in agreement with the standard model expectation R ( K ) ≈ 1 . This measurement is limited by the statistical precision of the electron channel. The integrated branching fraction in the same q 2 range, B ( B ± → K ± μ + μ − ) = ( 12.42 ± 0.68 ) × 10 − 8 , is consistent with the present world-average value and has a comparable precision.

The nuclear dependence of the inclusive inelastic electron scattering cross section (the EMC effect) has been measured for the first time in B10 and B11. Previous measurements of the EMC effect in A≤12 nuclei showed an unexpected nuclear dependence; B10 and B11 were measured to explore the EMC effect in this region in more detail. Results are presented for Be9, B10, B11, and C12 at an incident beam energy of 10.6 GeV. The EMC effect in the boron isotopes was found to be similar to that for Be9 and C12, yielding almost no nuclear dependence in the EMC effect in the range A=4–12. This represents important new data supporting the hypothesis that the EMC effect depends primarily on the local nuclear environment due to the cluster structure of these nuclei.Received 8 July 2022Revised 21 April 2023Accepted 17 July 2023DOI:https://doi.org/10.1103/PhysRevC.108.035201©2023 American Physical SocietyPhysics Subject Headings (PhySH)Research AreasLepton induced nuclear reactionsQCD in nuclear reactionsProperties6 ≤ A ≤ 19TechniquesParticle sources & targetsSpectrometers & spectroscopic techniquesNuclear Physics

Quasi-elastic scattering on $^{12}$C$(e,e'p)$ was measured in Hall C at Jefferson Lab for space-like 4-momentum transfer squared $Q^2$ in the range of 8--14.2\,(GeV/$c$)$^2$ with proton momenta up to 8.3\,GeV/$c$. The experiment was carried out in the upgraded Hall C at Jefferson Lab. It used the existing high momentum spectrometer and the new super high momentum spectrometer to detect the scattered electrons and protons in coincidence. The nuclear transparency was extracted as the ratio of the measured yield to the yield calculated in the plane wave impulse approximation. Additionally, the transparency of the $1s_{1/2}$ and $1p_{3/2}$ shell protons in $^{12}$C was extracted, and the asymmetry of the missing momentum distribution was examined for hints of the quantum chromodynamics prediction of Color Transparency. All of these results were found to be consistent with traditional nuclear physics and inconsistent with the onset of Color Transparency.

Quasielastic scattering on 12C(e, e'p) was measured in Hall C at Jefferson Lab for spacelike four-momentum transfer squared Q2 in the range of 8-14.2 (GeV/c)2 with proton momenta up to 8.3 GeV/c. The experiment was carried out in the upgraded Hall C at Jefferson Lab. It used the existing high-momentum spectrometer and the new super-high-momentum spectrometer to detect the scattered electrons and protons in coincidence. The nuclear transparency was extracted as the ratio of the measured yield to the yield calculated in the plane wave impulse approximation. Additionally, the transparency of the 1s1/2 and 1p3/2 shell protons in 12C was extracted, and the asymmetry of the missing momentum distribution was examined for hints of the quantum chromodynamics prediction of color transparency. All of these results were found to be consistent with traditional nuclear physics and inconsistent with the onset of color transparency.

The nuclear dependence of the inclusive inelastic electron scattering cross section (the EMC effect) has been measured for the first time in 10B and 11B. Previous measurements of the EMC effect in A 12 nuclei showed an unexpected nuclear dependence; 10B and 11B were measured to explore the EMC effect in this region in more detail. Results are presented for 9Be, 10B, 11B, and 12C at an incident beam energy of 10.6 GeV. The EMC effect in the boron isotopes was found to be similar to that for 9Be and 12C, yielding almost no nuclear dependence in the EMC effect in the range A = 4-12. This represents important new data supporting the hypothesis that the EMC effect depends primarily on the local nuclear environment due to the cluster structure of these nuclei.

Quasi-elastic scattering on 12 C( e, e (cid:48) p ) was measured in Hall C at Jefferson Lab for space-like 4-momentum transfer squared Q 2 in the range of 8–14.2 (GeV/ c ) 2 with proton momenta up to 8.3 GeV/ c . The experiment was carried out in the upgraded Hall C at Jefferson Lab. It used the existing high momentum spectrometer and the new super high momentum spectrometer to detect the scattered electrons and protons in coincidence. The nuclear transparency was extracted as the ratio of the measured yield to the yield calculated in the plane wave impulse approximation. Additionally, the transparency of the 1 s 1 / 2 and 1 p 3 / 2 shell protons in 12 C was extracted, and the asymmetry of the missing momentum distribution was examined for hints of the quantum chromodynamics prediction of Color Transparency. All of these results were found to be consistent with traditional nuclear physics and inconsistent with the onset of Color Transparency.

High precision measurements of the polarized electron beam-spin asymmetry in semi-inclusive deep inelastic scattering (SIDIS) from the proton have been performed using a 10.6 GeV incident electron beam and the CLAS12 spectrometer at Jefferson Lab. We report here a high precision multidimensional study of single π^{+} SIDIS data over a large kinematic range in Bjorken x, fractional energy, and transverse momentum of the hadron as well as photon virtualities Q^{2} ranging from 1-7  GeV^{2}. In particular, the structure function ratio F_{LU}^{sinϕ}/F_{UU} has been determined, where F_{LU}^{sinϕ} is a twist-3 quantity that can reveal novel aspects of emergent hadron mass and quark-gluon correlations within the nucleon. The data's impact on the evolving understanding of the underlying reaction mechanisms and their kinematic variation is explored using theoretical models for the different contributing transverse momentum dependent parton distribution functions.

The nuclear dependence of the inclusive inelastic electron scattering cross section (the EMC effect) has been measured for the first time in $^{10}$B and $^{11}$B. Previous measurements of the EMC effect in $A \leq 12$ nuclei showed an unexpected nuclear dependence; $^{10}$B and $^{11}$B were measured to explore the EMC effect in this region in more detail. Results are presented for $^9$Be, $^{10}$B, $^{11}$B, and $^{12}$C at an incident beam energy of 10.6~GeV. The EMC effect in the boron isotopes was found to be similar to that for $^9$Be and $^{12}$C, yielding almost no nuclear dependence in the EMC effect in the range $A=4-12$. This represents important, new data supporting the hypothesis that the EMC effect depends primarily on the local nuclear environment due to the cluster structure of these nuclei.

N. Liyanage, B. D. Anderson, K. A. Aniol, L. Auerbach, F. T. Baker, J. Berthot, W. Bertozzi, P. -Y. Bertin, L. Bimbot, W. U. Boeglin, E. J. Brash, V. Breton, H. Breuer, E. Burtin, J. R. Calarco, L. Cardman, G. D. Cates, C. Cavata, C. C. Chang, J. -P. Chen, E. Cisbani, D. S. Dale, R. De Leo, A. Deur, B. Diederich, P. Djawotho, J. Domingo, B. Doyle, J. -E. Ducret, M. B. Epstein, L. A. Ewell, J. M. Finn, K. G. Fissum, H. Fonvieille, B. Frois, S. Frullani, J. Gao, F. Garibaldi, A. Gasparian, S. Gilad, R. Gilman, A. Glamazdin, C. Glashausser, J. Gomez, V. Gorbenko, T. Gorringe, F. W. Hersman, R. Holmes, M. Holtrop, N. d’Hose, C. Howell, G. M. Huber, C. E. Hyde-Wright, M. Iodice, C. W. de Jager, S. Jaminion, M. K. Jones, K. Joo, C. Jutier, W. Kahl, S. Kato, J. J. Kelly, S. Kerhoas, M. Khandaker, M. Khayat, K. Kino, W. Korsch, L. Kramer, K. S. Kumar, G. Kumbartzki, G. Laveissière, A. Leone, J. J. LeRose, L. Levchuk, M. Liang, R. A. Lindgren, G. J. Lolos, R. W. Lourie, R. Madey, K. Maeda, S. Malov, D. M. Manley, D. J. Margaziotis P. Markowitz, J. Martino, J. S. McCarthy, K. McCormick, J. McIntyre, R. L. J. van der Meer, Z. -E. Meziani, R. Michaels, J. Mougey, S. Nanda, D. Neyret, E. A. J. M. Offermann, Z. Papandreou, C. F. Perdrisat, R. Perrino, G. G. Petratos, S. Platchkov, R. Pomatsalyuk, D. L. Prout, V. A. Punjabi, T. Pussieux, G. Quéméner, R. D. Ransome, O. Ravel, Y. Roblin, R. Roche, D. Rowntree, G.A. Rutledge, P. M. Rutt, A. Saha, T. Saito, A. J. Sarty, A. Serdarevic-Offermann, T. P. Smith, A. Soldi, P. Sorokin, P. Souder, R. Suleiman, J. A. Templon, T. Terasawa, L. Todor, H. Tsubota, H. Ueno, P. E. Ulmer, G.M. Urciuoli, P. Vernin, S. van Verst, B. Vlahovic, H. Voskanyan, J. W. Watson, L. B. Weinstein, K. Wijesooriya, R. Wilson, B. Wojtsekhowski, D. G. Zainea, V. Zeps, J. Zhao, Z. -L. Zhou

V. Sulkosky,1, 2, 3 C. Peng,4, 5 J.-P. Chen,2 A. Deur⇤,3, 2 S. Abrahamyan,6 K. A. Aniol,7 D. S. Armstrong,1 T. Averett,1 S. L. Bailey,1 A. Beck,8 P. Bertin,9 F. Butaru,10 W. Boeglin,11 A. Camsonne,9 G. D. Cates,3 C. C. Chang,12 Seonho Choi,10 E. Chudakov,2 L. Coman,11 J. C Cornejo,7 B. Craver,3 F. Cusanno,13 R. De Leo,14 C. W. de Jager†,2 J. D. Denton,15 S. Dhamija,16 R. Feuerbach,2 J. M. Finn†,1 S. Frullani†,17, 18 K. Fuoti,1 H. Gao,4 F. Garibaldi,17, 18 O. Gayou,8 R. Gilman,2, 19 A. Glamazdin,20 C. Glashausser,19 J. Gomez,2 J.-O. Hansen,2 D. Hayes,21 B. Hersman,22 D. W. Higinbotham,2 T. Holmstrom,1, 15 T. B. Humensky,3 C. E. Hyde,21 H. Ibrahim,21, 23 M. Iodice,13 X. Jiang,19 L. J. Kaufman,24 A. Kelleher,1 K. E. Keister,1 W. Kim,25 A. Kolarkar,16 N. Kolb,26 W. Korsch,16 K. Kramer,1, 4 G. Kumbartzki,19 L. Lagamba,14 V. Lainé,2, 9 G. Laveissiere,9 J. J. Lerose,2 D. Lhuillier,27 R. Lindgren,3 N. Liyanage,3, 2 H.-J. Lu,28 B. Ma,8 D. J. Margaziotis,7 P. Markowitz,11 K. McCormick,19 M. Meziane,4 Z.-E. Meziani,10 R. Michaels,2 B. Moffit,1 P. Monaghan,8 S. Nanda,2 J. Niedziela,24 M. Niskin,11 R. Pandolfi,29 K. D. Paschke,24 M. Potokar†,30 A. Puckett,3 V. A. Punjabi,31 Y. Qiang,8 R. Ransome,19 B. Reitz,2 R. Roché,32 A. Saha†,2 A. Shabetai,19 S. Širca,33 J. T. Singh,3 K. Slifer,10 R. Snyder,3 P. Solvignon†,10 R. Stringer,4 R. Subedi,34 W. A. Tobias,3 N. Ton,3 P. E. Ulmer,21 G. M. Urciuoli,13 A. Vacheret,27 E. Voutier,35 K. Wang,3 L. Wan,8 B. Wojtsekhowski,36 S. Woo,25 H. Yao,10 J. Yuan,19 X. Zhan,8 X. Zheng,5 and L. Zhu8

The observation of beam spin asymmetries in two-pion production in semi-inclusive deep inelastic scattering off an unpolarized proton target is reported. The data presented here were taken in the fall of 2018 with the CLAS12 spectrometer using a 10.6 GeV longitudinally spin-polarized electron beam delivered by CEBAF at JLab. The measured asymmetries provide the first opportunity to extract the parton distribution function e(x), which provides information about the interaction between gluons and quarks, in a collinear framework that offers cleaner access than previous measurements. The asymmetries also constitute the first ever signal sensitive to the helicity-dependent two-pion fragmentation function G_{1}^{⊥}. A clear sign change is observed around the ρ mass that appears in model calculations and is indicative of the dependence of the produced pions on the helicity of the fragmenting quark.

The (cid:12)rst ( ~e; e 0 ~p ) polarization transfer measurements on a nucleus heavier than deuterium have been carried out at Je(cid:11)erson Laboratory. Transverse and longitudinal components of the polarization of protons ejected in the reaction 16 O( ~e; e 0 ~p ) were measured in quasielastic perpendicular kinematics at a Q 2 of 0.8 (GeV/c) 2 . The data are in good agreement with state of the art calculations.

Quasielastic ^{12}C(e,e^{'}p) scattering was measured at spacelike 4-momentum transfer squared Q^{2}=8, 9.4, 11.4, and 14.2  (GeV/c)^{2}, the highest ever achieved to date. Nuclear transparency for this reaction was extracted by comparing the measured yield to that expected from a plane-wave impulse approximation calculation without any final state interactions. The measured transparency was consistent with no Q^{2} dependence, up to proton momenta of 8.5  GeV/c, ruling out the quantum chromodynamics effect of color transparency at the measured Q^{2} scales in exclusive (e,e^{'}p) reactions. These results impose strict constraints on models of color transparency for protons.

The observation of beam spin asymmetries in two-pion production in semi-inclusive deep inelastic scattering off an unpolarized proton target is reported. The data presented here were taken in the fall of 2018 with the CLAS12 spectrometer using a 10.6 GeV longitudinally spin-polarized electron beam delivered by CEBAF at JLab. The measured asymmetries provide the first opportunity to extract the parton distribution function e ð x Þ , which provides information about the interaction between gluons and quarks, in a collinear framework that offers cleaner access than previous measurements. The asymmetries also constitute the first ever signal sensitive to the helicity-dependent two-pion fragmentation function G ⊥ 1 . A clear sign change is observed around the ρ mass that appears in model calculations and is indicative of the dependence of the produced pions on the helicity of the fragmenting quark.

The spin-structure functions g_1 and g_2, and the spin-dependent partial cross-section \sigma_{TT} have been extracted from the polarized cross-sections differences, \Delta \sigma_{||}(\nu,Q^2) and \Delta \sigma_{\perp}(\nu,Q^2) measured for the 3He(e,e')X reaction at Jefferson Lab. Polarized electrons with energies from 1.147 to 4.404 GeV were scattered at angles of 6^o and 9^o from a longitudinally or transversely polarized 3He target. The data cover the kinematic regions of the quasi-elastic, resonance and beyond. From the extracted spin-structure functions, the first moments \Gamma_1(Q^2), \Gamma_2(Q^2) and I_{TT}(Q^2) are evaluated with high precision for the neutron in the Q^2 range from 0.035 to 0.24 GeV^2. Finally, these low Q^2 results are used to test chiral perturbation theory calculations.

The exclusive electroproduction process ep → e ′ p ′ π 0 was measured in the range of photon virtualities Q 2 = 0 . 4–1 . 0 GeV 2 and the invariant mass range of the p π 0 system of W = 1 . 1–1 . 8 GeV. These kinematics are covered in exclusive π 0 electroproduction off the proton with nearly complete angular coverage in the p π 0 center-of-mass system and with high statistical accuracy. Nearly 36 000 cross-section points were measured, and the structure functions σ T + ǫσ L , σ LT , and σ TT , were extracted via fitting the φ π 0 dependence of the cross section. A Legendre polynomial expansion analysis demonstrates the sensitivity of our data to high-lying N ∗ and (cid:6) ∗ resonances with M > 1 . 6 GeV. As part of a broad effort to determine the electrocouplings of the N ∗ and (cid:6) ∗ resonances using both single- and double-pion electroproduction, this dataset is crucial for the reliable extraction of the high-lying resonance electrocouplings from the combined isospin analysis of the N π and π + π − p channels.