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- 3 July 2023
- Published by Taylor & Francis in Nuclear Physics News
The Nuclear Physics Department of IRFU at CEA Paris-Saclay
by Hervé Moutarde, Frank Sabatié
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- 3 July 2023
- Published by Taylor & Francis in Nuclear Physics News
The Nuclear Physics Department of IRFU at CEA Paris-Saclay
by Hervé Moutarde, Frank Sabatié
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Cited by 267
- 20 February 2019
- Published by Springer Nature in Nature
Modified structure of protons and neutrons in correlated pairs
by The CLAS Collaboration, B. Schmookler, M. Duer, A. Schmidt, O. Hen, S. Gilad, E. Piasetzky, M. Strikman, L. B. Weinstein, S. Adhikari, et al.
The atomic nucleus is made of protons and neutrons (nucleons), which are themselves composed of quarks and gluons. Understanding how the quark–gluon structure of a nucleon bound in an atomic nucleus is modified by the surrounding nucleons is an outstanding challenge. Although evidence for such modification—known as the EMC effect—was first observed over 35 years ago, there is still no generally accepted explanation for its cause^1,2,3. Recent observations suggest that the EMC effect is related to close-proximity short-range correlated (SRC) nucleon pairs in nuclei^4,5. Here we report simultaneous, high-precision measurements of the EMC effect and SRC abundances. We show that EMC data can be explained by a universal modification of the structure of nucleons in neutron–proton SRC pairs and present a data-driven extraction of the corresponding universal modification function. This implies that in heavier nuclei with many more neutrons than protons, each proton is more likely than each neutron to belong to an SRC pair and hence to have distorted quark structure. This universal modification function will be useful for determining the structure of the free neutron and thereby testing quantum chromodynamics symmetry-breaking mechanisms and may help to discriminate between nuclear physics effects and beyond-the-standard-model effects in neutrino experiments.
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- 20 February 2019
- Published by Springer Nature in Nature
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Modified structure of protons and neutrons in correlated pairs
by The CLAS Collaboration, B. Schmookler, M. Duer, A. Schmidt, O. Hen, S. Gilad, E. Piasetzky, M. Strikman, L. B. Weinstein, S. Adhikari, et al.
The atomic nucleus is made of protons and neutrons (nucleons), which are themselves composed of quarks and gluons. Understanding how the quark–gluon structure of a nucleon bound in an atomic nucleus is modified by the surrounding nucleons is an outstanding challenge. Although evidence for such modification—known as the EMC effect—was first observed over 35 years ago, there is still no generally accepted explanation for its cause^1,2,3. Recent observations suggest that the EMC effect is related to close-proximity short-range correlated (SRC) nucleon pairs in nuclei^4,5. Here we report simultaneous, high-precision measurements of the EMC effect and SRC abundances. We show that EMC data can be explained by a universal modification of the structure of nucleons in neutron–proton SRC pairs and present a data-driven extraction of the corresponding universal modification function. This implies that in heavier nuclei with many more neutrons than protons, each proton is more likely than each neutron to belong to an SRC pair and hence to have distorted quark structure. This universal modification function will be useful for determining the structure of the free neutron and thereby testing quantum chromodynamics symmetry-breaking mechanisms and may help to discriminate between nuclear physics effects and beyond-the-standard-model effects in neutrino experiments.
Cited by 267
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Cited by 11
- 1 February 2019
- Published by Elsevier in Physics Letters B
Measurement of the beam spin asymmetry of $\vec{e} p \to e^{'} p^{'} η$ in the deep-inelastic regime with CLAS
by B. Zhao, A. Kim, K. Joo, I. Bedlinskiy, W. Kim, V. Kubarovsky, M. Ungaro, S. Adhikari, Z. Akbar, G. Angelini, et al.
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- 1 February 2019
- Published by Elsevier in Physics Letters B
Open Access
Measurement of the beam spin asymmetry of $\vec{e} p \to e^{'} p^{'} η$ in the deep-inelastic regime with CLAS
by B. Zhao, A. Kim, K. Joo, I. Bedlinskiy, W. Kim, V. Kubarovsky, M. Ungaro, S. Adhikari, Z. Akbar, G. Angelini, et al.
Cited by 11
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Cited by 49
- 1 January 2019
- Published by Elsevier in Physics Letters B
First results on nucleon resonance photocouplings from the γp → π+π−p reaction
by E. Golovatch, V.D. Burkert, D.S. Carman, R.W. Gothe, K. Hicks, B.S. Ishkhanov, V.I. Mokeev, E. Pasyuk, S. Adhikari, Z. Akbar, et al.
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- 1 January 2019
- Published by Elsevier in Physics Letters B
Open Access
First results on nucleon resonance photocouplings from the γp → π+π−p reaction
by E. Golovatch, V.D. Burkert, D.S. Carman, R.W. Gothe, K. Hicks, B.S. Ishkhanov, V.I. Mokeev, E. Pasyuk, S. Adhikari, Z. Akbar, et al.
Cited by 49
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Cited by 14
- 27 December 2018
- Published by American Physical Society (APS) in Physical Review C
$Ξ^{*}$ photoproduction from threshold to $W = 3.3 GeV$
by J. T. Goetz, K. Hicks, M. C. Kunkel, J. W. Price, D. P. Weygand, S. Adhikari, S. Anefalos Pereira, M. Battaglieri, I. Bedlinskiy, A. S. Biselli, et al.
The doubly strange $Ξ$ baryons provide an effective way to study a puzzle called the missing-baryons problem where both quark models and lattice gauge theory predict more baryon excited states than are seen experimentally. However, few of these excited states have been observed with any certainty. Here, high-mass $Ξ^{*}$ states have been searched for in photoproduction with the detector of the CLAS Collaboration, and upper limits for the total cross sections have been established from threshold to $W = 3.3 GeV$ . In addition, the total cross sections of the ground-state $Ξ^{-}$ (1320) and first excited state $Ξ^{-}$ (1530) are presented, extending significantly the center-of-mass energy range of previous data.
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- 27 December 2018
- Published by American Physical Society (APS) in Physical Review C
Open Access
$Ξ^{*}$ photoproduction from threshold to $W = 3.3 GeV$
by J. T. Goetz, K. Hicks, M. C. Kunkel, J. W. Price, D. P. Weygand, S. Adhikari, S. Anefalos Pereira, M. Battaglieri, I. Bedlinskiy, A. S. Biselli, et al.
The doubly strange $Ξ$ baryons provide an effective way to study a puzzle called the missing-baryons problem where both quark models and lattice gauge theory predict more baryon excited states than are seen experimentally. However, few of these excited states have been observed with any certainty. Here, high-mass $Ξ^{*}$ states have been searched for in photoproduction with the detector of the CLAS Collaboration, and upper limits for the total cross sections have been established from threshold to $W = 3.3 GeV$ . In addition, the total cross sections of the ground-state $Ξ^{-}$ (1320) and first excited state $Ξ^{-}$ (1530) are presented, extending significantly the center-of-mass energy range of previous data.
Cited by 14
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Cited by 15
- 19 October 2018
- Published by American Physical Society (APS) in Physical Review C
Beam-target helicity asymmetry $E$ in $K^{0} Λ$ and $K^{0} Σ^{0}$ photoproduction on the neutron
by D. H. Ho, R. A. Schumacher, A. D'ANgelo, A. Deur, J. Fleming, C. Hanretty, T. Kageya, F. J. Klein, E. Klempt, M. M. Lowry, et al.
We report the first measurements of the $E$ beam-target helicity asymmetry for the $\vec{γ} \vec{n} \to K^{0} Λ$ and $K^{0} Σ^{0}$ channels in the energy range $1.70 \leq W \leq 2.34$ GeV. The CLAS system at Jefferson Lab uses a circularly polarized photon beam and a target consisting of longitudinally polarized solid molecular hydrogen deuteride with low background contamination for the measurements. The multivariate analysis method boosted decision trees is used to isolate the reactions of interest. Comparisons with predictions from the KaonMAID, SAID, and Bonn-Gatchina models are presented. These results will help separate the isospin $I = 0$ and $I = 1$ photocoupling transition amplitudes in pseudoscalar meson photoproduction.
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- 19 October 2018
- Published by American Physical Society (APS) in Physical Review C
Open Access
Beam-target helicity asymmetry $E$ in $K^{0} Λ$ and $K^{0} Σ^{0}$ photoproduction on the neutron
by D. H. Ho, R. A. Schumacher, A. D'ANgelo, A. Deur, J. Fleming, C. Hanretty, T. Kageya, F. J. Klein, E. Klempt, M. M. Lowry, et al.
We report the first measurements of the $E$ beam-target helicity asymmetry for the $\vec{γ} \vec{n} \to K^{0} Λ$ and $K^{0} Σ^{0}$ channels in the energy range $1.70 \leq W \leq 2.34$ GeV. The CLAS system at Jefferson Lab uses a circularly polarized photon beam and a target consisting of longitudinally polarized solid molecular hydrogen deuteride with low background contamination for the measurements. The multivariate analysis method boosted decision trees is used to isolate the reactions of interest. Comparisons with predictions from the KaonMAID, SAID, and Bonn-Gatchina models are presented. These results will help separate the isospin $I = 0$ and $I = 1$ photocoupling transition amplitudes in pseudoscalar meson photoproduction.
Cited by 15
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Cited by 19
- 9 October 2018
- Published by American Physical Society (APS) in Physical Review C
Measurement of unpolarized and polarized cross sections for deeply virtual Compton scattering on the proton at Jefferson Laboratory with CLAS
by N. Hirlinger Saylor, B. Guegan, V. D. Burkert, L. Elouadrhiri, M. Garçon, F. X. Girod, M. Guidal, H. S. Jo, V. Kubarovsky, S. Niccolai, et al.
This paper reports the measurement of polarized and unpolarized cross sections for the $e p \to e^{'} p^{'} γ$ reaction, which is composed of deeply virtual Compton scattering (DVCS) and Bethe-Heitler (BH) processes, at an electron beam energy of 5.88 GeV at the Thomas Jefferson National Accelerator Facility using the Large Acceptance Spectrometer CLAS. The unpolarized cross sections and polarized cross section differences have been measured over broad kinematics, $0.10 < x_{B} < 0.58, 1.0 < Q^{2} < 4.8 {GeV}^{2}$ , and $0.09 < - t < 2.00 {GeV}^{2}$ . The results are found to be consistent with previous CLAS data, and these new data are discussed in the framework of the generalized parton distribution approach. Calculations with two widely used phenomenological models are approximately compatible with the experimental results over a large portion of the kinematic range of the data.
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- 9 October 2018
- Published by American Physical Society (APS) in Physical Review C
Open Access
Measurement of unpolarized and polarized cross sections for deeply virtual Compton scattering on the proton at Jefferson Laboratory with CLAS
by N. Hirlinger Saylor, B. Guegan, V. D. Burkert, L. Elouadrhiri, M. Garçon, F. X. Girod, M. Guidal, H. S. Jo, V. Kubarovsky, S. Niccolai, et al.
This paper reports the measurement of polarized and unpolarized cross sections for the $e p \to e^{'} p^{'} γ$ reaction, which is composed of deeply virtual Compton scattering (DVCS) and Bethe-Heitler (BH) processes, at an electron beam energy of 5.88 GeV at the Thomas Jefferson National Accelerator Facility using the Large Acceptance Spectrometer CLAS. The unpolarized cross sections and polarized cross section differences have been measured over broad kinematics, $0.10 < x_{B} < 0.58, 1.0 < Q^{2} < 4.8 {GeV}^{2}$ , and $0.09 < - t < 2.00 {GeV}^{2}$ . The results are found to be consistent with previous CLAS data, and these new data are discussed in the framework of the generalized parton distribution approach. Calculations with two widely used phenomenological models are approximately compatible with the experimental results over a large portion of the kinematic range of the data.
Cited by 19
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Cited by 10
- 27 September 2018
- Published by American Physical Society (APS) in Physical Review D
Photoproduction of $K^{+} K^{-}$ meson pairs on the proton
by S. Lombardo, M. Battaglieri, A. Celentano, A. D’aNgelo, R. De Vita, A. Filippi, D. I. Glazier, S. M. Hughes, V. Mathieu, A. Rizzo, et al.
The exclusive reaction $γ p \to p K^{+} K^{-}$ was studied in the photon energy range $3.0 - 3.8 GeV$ and momentum transfer range $0.6 < - t < 1.3 {GeV}^{2}$ . Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. In this kinematic range the integrated luminosity was approximately $20 {pb}^{- 1}$ . The reaction was isolated by detecting the $K^{+}$ and the proton in CLAS, and reconstructing the $K^{-}$ via the missing-mass technique. Moments of the dikaon decay angular distributions were extracted from the experimental data. Besides the dominant contribution of the $ϕ$ meson in the $P$ wave, evidence for $S - P$ interference was found. The differential production cross sections $d σ / d t$ for individual waves in the mass range of the $ϕ$ resonance were extracted and compared to predictions of a Regge-inspired model. This is the first time the $t$ -dependent cross section of the $S$ -wave contribution to the elastic $K^{+} K^{-}$ photoproduction has been measured.
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- 27 September 2018
- Published by American Physical Society (APS) in Physical Review D
Open Access
Photoproduction of $K^{+} K^{-}$ meson pairs on the proton
by S. Lombardo, M. Battaglieri, A. Celentano, A. D’aNgelo, R. De Vita, A. Filippi, D. I. Glazier, S. M. Hughes, V. Mathieu, A. Rizzo, et al.
The exclusive reaction $γ p \to p K^{+} K^{-}$ was studied in the photon energy range $3.0 - 3.8 GeV$ and momentum transfer range $0.6 < - t < 1.3 {GeV}^{2}$ . Data were collected with the CLAS detector at the Thomas Jefferson National Accelerator Facility. In this kinematic range the integrated luminosity was approximately $20 {pb}^{- 1}$ . The reaction was isolated by detecting the $K^{+}$ and the proton in CLAS, and reconstructing the $K^{-}$ via the missing-mass technique. Moments of the dikaon decay angular distributions were extracted from the experimental data. Besides the dominant contribution of the $ϕ$ meson in the $P$ wave, evidence for $S - P$ interference was found. The differential production cross sections $d σ / d t$ for individual waves in the mass range of the $ϕ$ resonance were extracted and compared to predictions of a Regge-inspired model. This is the first time the $t$ -dependent cross section of the $S$ -wave contribution to the elastic $K^{+} K^{-}$ photoproduction has been measured.
Cited by 10
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Cited by 90
- 31 August 2018
- Published by American Physical Society (APS) in Physical Review Letters
Center of Mass Motion of Short-Range Correlated Nucleon Pairs studied via the $A (e, e^{'} p p)$ Reaction
by E. O. Cohen, O. Hen, E. Piasetzky, L. B. Weinstein, M. Duer, A. Schmidt, I. Korover, H. Hakobyan, S. Adhikari, Z. Akbar, et al.
Short-range correlated (SRC) nucleon pairs are a vital part of the nucleus, accounting for almost all nucleons with momentum greater than the Fermi momentum ( $k_{F}$ ). A fundamental characteristic of SRC pairs is having large relative momenta as compared to $k_{F}$ , and smaller center of mass (c.m.) which indicates a small separation distance between the nucleons in the pair. Determining the c.m. momentum distribution of SRC pairs is essential for understanding their formation process. We report here on the extraction of the c.m. motion of proton-proton ( $p p$ ) SRC pairs in carbon and, for the first time in heavier and ansymetric nuclei: aluminum, iron, and lead, from measurements of the $A (e, e^{'} p p)$ reaction. We find that the pair c.m. motion for these nuclei can be described by a three-dimensional Gaussian with a narrow width ranging from 140 to $170 MeV / c$ , approximately consistent with the sum of two mean-field nucleon momenta. Comparison with calculations appears to show that the SRC pairs are formed from mean-field nucleons in specific quantum states.
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- 31 August 2018
- Published by American Physical Society (APS) in Physical Review Letters
Open Access
Center of Mass Motion of Short-Range Correlated Nucleon Pairs studied via the $A (e, e^{'} p p)$ Reaction
by E. O. Cohen, O. Hen, E. Piasetzky, L. B. Weinstein, M. Duer, A. Schmidt, I. Korover, H. Hakobyan, S. Adhikari, Z. Akbar, et al.
Short-range correlated (SRC) nucleon pairs are a vital part of the nucleus, accounting for almost all nucleons with momentum greater than the Fermi momentum ( $k_{F}$ ). A fundamental characteristic of SRC pairs is having large relative momenta as compared to $k_{F}$ , and smaller center of mass (c.m.) which indicates a small separation distance between the nucleons in the pair. Determining the c.m. momentum distribution of SRC pairs is essential for understanding their formation process. We report here on the extraction of the c.m. motion of proton-proton ( $p p$ ) SRC pairs in carbon and, for the first time in heavier and ansymetric nuclei: aluminum, iron, and lead, from measurements of the $A (e, e^{'} p p)$ reaction. We find that the pair c.m. motion for these nuclei can be described by a three-dimensional Gaussian with a narrow width ranging from 140 to $170 MeV / c$ , approximately consistent with the sum of two mean-field nucleon momenta. Comparison with calculations appears to show that the SRC pairs are formed from mean-field nucleons in specific quantum states.
Cited by 90
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Cited by 30
- 21 August 2018
- Published by American Physical Society (APS) in Physical Review C
Measurements of the $γ_{v} p \to p^{'} π^{+} π^{-}$ cross section with the CLAS detector for $0.4 {GeV}^{2} < Q^{2} < 1.0 {GeV}^{2}$ and $1.3 GeV < W < 1.825 GeV$
by G. V. Fedotov, Iu. A. Skorodumina, V. D. Burkert, R. W. Gothe, K. Hicks, V. I. Mokeev, S. Adhikari, Whitney R. Armstrong, H. Avakian, J. Ball, et al.
New results on the single-differential and fully integrated cross sections for the process $γ_{v} p \to p^{'} π^{+} π^{-}$ are presented. The experimental data were collected with the CLAS detector at Jefferson Laboratory. Measurements were carried out in the kinematic region of the reaction invariant mass $W$ from 1.3 to 1.825 GeV and the photon virtuality $Q^{2}$ from 0.4 to 1.0 ${GeV}^{2}$ . The cross sections were obtained in narrow $Q^{2}$ bins (0.05 ${GeV}^{2}$ ) with the smallest statistical uncertainties achieved in double-pion electroproduction experiments to date. The results were found to be in agreement with previously available data where they overlap. A preliminary interpretation of the extracted cross sections, which was based on a phenomenological meson-baryon reaction model, revealed substantial relative contributions from nucleon resonances. The data offer promising prospects to improve knowledge on the $Q^{2}$ evolution of the electrocouplings of most resonances with masses up to $\sim 1.8$ GeV.
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- 21 August 2018
- Published by American Physical Society (APS) in Physical Review C
Open Access
Measurements of the $γ_{v} p \to p^{'} π^{+} π^{-}$ cross section with the CLAS detector for $0.4 {GeV}^{2} < Q^{2} < 1.0 {GeV}^{2}$ and $1.3 GeV < W < 1.825 GeV$
by G. V. Fedotov, Iu. A. Skorodumina, V. D. Burkert, R. W. Gothe, K. Hicks, V. I. Mokeev, S. Adhikari, Whitney R. Armstrong, H. Avakian, J. Ball, et al.
New results on the single-differential and fully integrated cross sections for the process $γ_{v} p \to p^{'} π^{+} π^{-}$ are presented. The experimental data were collected with the CLAS detector at Jefferson Laboratory. Measurements were carried out in the kinematic region of the reaction invariant mass $W$ from 1.3 to 1.825 GeV and the photon virtuality $Q^{2}$ from 0.4 to 1.0 ${GeV}^{2}$ . The cross sections were obtained in narrow $Q^{2}$ bins (0.05 ${GeV}^{2}$ ) with the smallest statistical uncertainties achieved in double-pion electroproduction experiments to date. The results were found to be in agreement with previously available data where they overlap. A preliminary interpretation of the extracted cross sections, which was based on a phenomenological meson-baryon reaction model, revealed substantial relative contributions from nucleon resonances. The data offer promising prospects to improve knowledge on the $Q^{2}$ evolution of the electrocouplings of most resonances with masses up to $\sim 1.8$ GeV.
Cited by 30

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