VECTOR MESON MODIFICATION IN NUCLEAR MATTER AT CLAS

Photoproduction of vector mesons off nuclei were performed at Jefferson Lab using the CEBAF Large Acceptance Spectrometer (CLAS). The properties of the ρ vector mesons were investigated via their rare leptonic decay to e+e−. After subtracting the combinatorial background, the ρ meson mass distributions were extracted for each of the targets. We observe no effects on the mass of the ρ meson, some widening in titanium and iron is observed consistent with the collisional broadening.

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DIELECTRON SPECTROSCOPY IN COLD NUCLEAR MATTER

International Journal of Modern Physics A ◽

10.1142/s0217751x11052694 ◽

2011 ◽

Vol 26 (03n04) ◽

pp. 737-740 ◽

Cited By ~ 2

Author(s):

◽

MICHAEL WEBER

Keyword(s):

Vector Meson ◽

Nuclear Matter ◽

Invariant Mass ◽

Meson Production ◽

Yield Ratio ◽

Vector Meson Production ◽

Production Threshold ◽

Light Vector Meson ◽

Mass Distributions ◽

Light Vector

We report recent data on e + e - pair emission in proton nucleus collisions at energies slightly above the light vector meson production threshold. Invariant mass distributions for the p + Nb system at Ekin = 3.5 GeV/c2 show a clear ρ/ω signal and are compared to data from elementary p + p reactions. We observe a constant π0/ω yield ratio for both systems.

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SEARCH FOR IN-MEDIUM MODIFICATIONS OF THE ρ MESON

International Journal of Modern Physics A ◽

10.1142/s0217751x07035562 ◽

2007 ◽

Vol 22 (02n03) ◽

pp. 380-387 ◽

Cited By ~ 4

Author(s):

◽

D. P. WEYGAND ◽

C. DJALALI ◽

R. NASSERIPOUR ◽

M. WOOD

Keyword(s):

Spectral Function ◽

Vector Mesons ◽

Medium Effects ◽

Final State ◽

Collisional Broadening ◽

Final State Interactions ◽

Medium Modifications ◽

Carbon Iron ◽

Large Acceptance ◽

Nuclear Effects

The photoproduction of vector mesons on various nuclei has been studied using the Cebaf Large Acceptance Spectrometer (CLAS) at Jefferson Laboratory, and here we present preliminary results. All three vector mesons, ρ, ω, and ϕ, are observed via their decay to e+e-, in order to reduce the effects of final state interactions in the nucleus. Of particular interest is possible in-medium effects on the properties of the ρ meson. The ρ spectral function is extracted from the data on various nuclei, carbon, iron, and titanium, and compared to the spectrum from liquid deuterium, which is relatively free of nuclear effects. We observe no effects on the mass of the ρ meson, however, there is some widening of the resonance in titanium and iron, which is consistent with expected collisional broadening.

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MEDIUM MODIFICATIONS OF LIGHT VECTOR MESONS IN PHOTOPRODUCTION REACTIONS AT JLAB

International Journal of Modern Physics A ◽

10.1142/s0217751x09043626 ◽

2009 ◽

Vol 24 (02n03) ◽

pp. 309-316

Author(s):

◽

M. H. WOOD ◽

C. DJALALI ◽

R. NASSERIPOUR ◽

D. WEYGAND

Keyword(s):

Mass Spectrum ◽

Nuclear Matter ◽

Mass Spectra ◽

Decay Channel ◽

Theoretical Calculations ◽

Meson Mass ◽

Vector Mesons ◽

Small Shift ◽

Light Vector ◽

Dense Nuclear Matter

Theoretical calculations predict the modification of properties of vector mesons, such as a shift in their masses and/or broadening of their widths in dense nuclear matter. These effects can be related to partial restoration of chiral symmetry at high density or temperature. The light vector mesons (ρ, ω, and ϕ) were photo-produced on 2 H , C , Ti , Fe , and Pb targets at the Thomas Jefferson National Laboratory using the CEBAF Large Acceptance Spectrometer (CLAS). The data were taken with a beam of tagged photons with energies up to 4 GeV. The properties of the ρ vector meson at normal nuclear densities and zero temperature,were investigated via their rare leptonic decay to e+e-. This decay channel is preferred over hadronic modes in order to eliminate final state interactions in the nuclear matter. A combinatorial background was subtracted from the invariant mass spectra using a well-established event-mixing technique. The ρ meson mass spectrum was extracted after the ω and ϕ signals were removed in a nearly model-independent way. The rho meson mass distributions were extracted for each of the targets. Comparisons were made between the ρ mass spectra from the heavy targets ( A > 2) with the mass spectrum extracted from the deuterium target. With respect to the ρ-meson mass, we obtain a small shift compatible with zero. Also, we measure widths consistent with standard nuclear many-body effects such as collisional broadening and Fermi motion. In this experiment, due to the long lifetimes and momenta greater than 0.8 GeV, the ω and ϕ mesons have a high probability of decaying outside the nucleus in their vacuum state. However, their in-medium widths can be accessed through their absorption inside the nucleus. Preliminary results on the ratios of the nuclear transparencies of the ω and ϕ mesons as a function of the number of target nucleons A, have been obtained and indicate a substantial widening in the medium.

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Measurement of Vector Meson Mass in Nuclear Matter at J-PARC

Proceedings of the 8th International Conference on Quarks and Nuclear Physics (QNP2018) ◽

10.7566/jpscp.26.024005 ◽

2019 ◽

Author(s):

Sakiko Ashikaga ◽

Kazuya Aoki ◽

Tatsuya Chujo ◽

Hideto En’yo ◽

Shinichi Esumi ◽

...

Keyword(s):

Vector Meson ◽

Nuclear Matter ◽

Meson Mass

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MODIFIED FORM OF VECTOR MESON COUPLING TO STUDY NUCLEAR MATTER AND ITS PHASE TRANSITION TO QUARK MATTER

International Journal of Modern Physics A ◽

10.1142/s0217751x00001294 ◽

2000 ◽

Vol 15 (21) ◽

pp. 3303-3313

Author(s):

BINAY MALAKAR

Keyword(s):

Phase Transition ◽

Energy Density ◽

Vector Meson ◽

Nuclear Matter ◽

Quark Matter ◽

Mean Field Theory ◽

Mean Field ◽

Theoretic Model ◽

Vector Mesons ◽

Scalar Type

In the proposed field theoretic model to study nuclear matter and its phase transition to quark matter, vector mesons (ωμ) have the usual coupling to fermionic currents and also scalar type coupling involving ωμωμ with fermionic fields and scalar mesons. The effect of this modified vector meson interaction for cold symmetric nuclear matter is investigated using relativistic mean-field theory. One of the striking features of the model is that at extremely high density part of the energy density due to vector mesons is proportional to the density ρ (instead of ρ2 as in Walecka model, Boguta model etc.) where Fermi gas energy density varies as ρ4/3.

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Vector and axial-vector mesons in nuclear matter

Physical Review D ◽

10.1103/physrevd.104.054005 ◽

2021 ◽

Vol 104 (5) ◽

Author(s):

Ralf-Arno Tripolt ◽

Christopher Jung ◽

Lorenz von Smekal ◽

Jochen Wambach

Keyword(s):

Nuclear Matter ◽

Axial Vector ◽

Vector Mesons

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Studying neutron structure at Jefferson Lab through electron scattering off the deuteron, using CLAS12 and the Central Neutron Detector

Journal of Physics Conference Series ◽

10.1088/1742-6596/1643/1/012191 ◽

2020 ◽

Vol 1643 (1) ◽

pp. 012191

Author(s):

Paul Naidoo ◽

Daria Sokhan ◽

Pierre Chatagnon ◽

Silvia Niccolai ◽

Katheryne Price

Keyword(s):

Neutron Detector ◽

Meson Production ◽

Deeply Virtual Compton Scattering ◽

Virtual Compton Scattering ◽

High Energy ◽

Neutral Meson ◽

Deuteron Target ◽

Jefferson Lab ◽

3D Tomography ◽

Large Acceptance

Abstract Generalised Parton Distributions (GPDs) offer a way of imaging nucleons through 3D tomography. They can be accessed experimentally in processes such as Deeply Virtual Compton Scattering (DVCS) and Deeply Virtual Meson Production (DVMP), where a high energy electron scatters from a quark inside a nucleon and a high energy photon or meson is produced as a result. Jefferson Lab has recently completed its energy upgrade and Hall B houses the new, large-acceptance CLAS12 detector array optimised for measurements of DVCS and DVMP in the newly accessible kinematic regime. Measurements on the proton and neutron are complementary and both are necessary to facilitate access to the full set of GPDs and enable their flavour separation. Neutron DVCS and DVMP are possible with the use of a deuteron target – the first CLAS12 experiment with which has started taking data this year. To enable exclusive reconstruction of DVCS and neutral-meson DVMP, a dedicated detector for recoiling neutrons – the Central Neutron Detector (CND) – was integrated into CLAS12. We present the first CLAS12 deuteron-target experiment, with a focus on the performance of the CND.

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