-
R. Gilman,
E. J. Downie,
G. Ron,
A. Afanasev,
J. Arrington,
O. Ates,
F. Benmokhtar,
J. Bernauer,
E. Brash,
W. J. Briscoe, [......],
A. Richter,
A. Sarty,
E. Schulte,
Y. Shamai,
N. Sparveris,
S. Strauch,
V. Sulkosky,
A. S. Tadepalli,
M. Taragin,
L. Weinstein
[show abstract]
[hide abstract]
ABSTRACT: The Proton Radius Puzzle is the inconsistency between the proton radius
determined from muonic hydrogen and the proton radius determined from atomic
hydrogen level transitions and ep elastic scattering. No generally accepted
resolution to the Puzzle has been found. Possible solutions generally fall into
one of three categories: the two radii are different due to novel
beyond-standard-model physics, the two radii are different due to novel aspects
of nucleon structure, and the two radii are the same, but there are
underestimated uncertainties or other issues in the ep experiments.
The MUon proton Scattering Experiment (MUSE) at the Paul Scherrer Institut is
a simultaneous measurement of \mu^+ p and e^+ p elastic scattering, as well as
\mu^- p and e^- p elastic scattering, which will allow a determination of the
consistency of the \mu p and the ep interactions. The differences between + and
- charge scattering are sensitive to two-photon exchange effects, higher-order
corrections to the scattering process. The slopes of the cross sections as Q^2
-> 0 determine the proton "radius". We plan to measure relative cross sections
at a typical level of a few tenths of a percent, which should allow the proton
radius to be determined at the level of ~0.01 fm, similar to previous ep
measurements. The measurements will test several possible explanations of the
proton radius puzzle, including some models of beyond-standard-model physics,
some models of novel hadronic physics, and some issues in the radius extraction
from scattering data.
03/2013;
-
C. S. Nepali,
M. Amaryan,
K. P. Adhikari,
M. Aghasyan,
S. Anefalos Pereira,
H. Baghdasaryan,
J. Ball,
M. Battaglieri,
V. Batourine,
I. Bedlinskiy, [......],
E. Voutier,
N. K. Walford,
D. P. Watts,
L. B. Weinstein,
D. P. Weygand,
N. Zachariou,
L. Zana,
J. Zhang,
Z. W. Zhao,
I. Zonta
[show abstract]
[hide abstract]
ABSTRACT: Experimental results on the $\Sigma^+(1189)$ hyperon transverse polarization
in photoproduction on a hydrogen target using the CLAS detector at Jefferson
laboratory are presented. The $\Sigma^+(1189)$ was reconstructed in the
exclusive reaction $\gamma+p\rightarrow K^{0}_{S} + \Sigma^+(1189)$ via the
$\Sigma^{+} \to p \pi^{0}$ decay mode. The $K^{0}_S$ was reconstructed in the
invariant mass of two oppositely charged pions with the $\pi^0$ identified in
the missing mass of the detected $p\pi^+\pi^-$ final state. Experimental data
were collected in the photon energy range $E_{\gamma}$ = 1.0-3.5 GeV
($\sqrt{s}$ range 1.66-2.73 GeV). We observe a large negative polarization of
up to 95%. As the mechanism of transverse polarization of hyperons produced in
unpolarized photoproduction experiments is still not well understood, these
results will help to distinguish between different theoretical models on
hyperon production and provide valuable information for the searches of missing
baryon resonances.
02/2013;
-
P. Khetarpal,
P. Stoler,
I. G. Aznauryan,
V. Kubarovsky,
K. P. Adhikari,
D. Adikaram,
M. Aghasyan,
M. J. Amaryan,
M. D. Anderson,
S. Anefalos Pereira, [......],
H. Voskanyan,
E. Voutier,
N. K. Walford,
L. B. Weinstein,
D. P. Weygand,
M. H. Wood,
N. Zachariou,
J. Zhang,
Z. W. Zhao,
I. Zonta
[show abstract]
[hide abstract]
ABSTRACT: We report the measurement of near threshold neutral pion electroproduction
cross sections and the extraction of the associated structure functions on the
proton in the kinematic range $Q^2$ from 2 to 4.5 GeV$^2$ and $W$ from 1.08 to
1.16 GeV. These measurements allow us to access the dominant pion-nucleon
s-wave multipoles $E_{0+}$ and $S_{0+}$ in the near-threshold region. In the
light-cone sum-rule framework (LCSR), these multipoles are related to the
generalized form factors $G_1^{\pi^0 p}(Q^2)$ and $G_2^{\pi^0 p}(Q^2)$. The
data are compared to these generalized form factors and the results for
$G_1^{\pi^0 p}(Q^2)$ are found to be in good agreement with the LCSR
predictions, but the level of agreement with $G_2^{\pi^0 p}(Q^2)$ is poor.
11/2012;
-
CLAS Collaboration,
I. Bedlinskiy,
V. Kubarovsky,
S. Niccolai,
P. Stoler,
K. P. Adhikari,
M. Aghasyan,
M. J. Amaryan,
M. Anghinolfi,
H. Avakian, [......],
E. Voutier,
N. K. Walford,
D. P. Watts,
L. B. Weinstein,
D. P. Weygand,
M. H. Wood,
N. Zachariou,
J. Zhang,
Z. W. Zhao,
I. Zonta
[show abstract]
[hide abstract]
ABSTRACT: Exclusive $\pi^0$ electroproduction at a beam energy of 5.75 GeV has been
measured with the Jefferson Lab CLAS spectrometer. Differential cross sections
were measured at more than 1800 kinematic values in $Q^2$, $x_B$, $t$, and
$\phi_\pi$, in the $Q^2$ range from 1.0 to 4.6 GeV$^2$,\ $-t$ up to 2 GeV$^2$,
and $x_B$ from 0.1 to 0.58. Structure functions $\sigma_T +\epsilon \sigma_L,
\sigma_{TT}$ and $\sigma_{LT}$ were extracted as functions of $t$ for each of
17 combinations of $Q^2$ and $x_B$. The data were compared directly with two
handbag-based calculations including both longitudinal and transversity GPDs.
Inclusion of only longitudinal GPDs very strongly underestimates $\sigma_T
+\epsilon \sigma_L$ and fails to account for $\sigma_{TT}$ and $\sigma_{LT}$,
while inclusion of transversity GPDs brings the calculations into substantially
better agreement with the data. There is very strong sensitivity to the
relative contributions of nucleon helicity flip and helicity non-flip
processes. The results confirm that exclusive $\pi^0$ electroproduction offers
direct experimental access to the transversity GPDs.
06/2012;
-
H. Baghdasaryan,
L. B. Weinstein,
J. M. Laget,
K. P. Adhikari,
M. Aghasyan,
M. J. Amaryan,
M. Anghinolfi,
J. Ball,
M. Battaglieri,
A. S. Biselli, [......],
S. Stepanyan,
S. Strauch,
M. Taiuti,
W. Tang,
S. Tkachenko,
H. Voskanyan,
E. Voutier,
M. H. Wood,
L. Zana,
B. Zhao
[show abstract]
[hide abstract]
ABSTRACT: Measuring nucleon-nucleon short range correlations (SRCs) has been a goal of the nuclear physics community for many years. They are an important part of the nuclear wave function, accounting for almost all of the high-momentum strength. They are closely related to the EMC effect. While their overall probability has been measured, measuring their momentum distributions is more difficult. In order to determine the best configuration for studying SRC momentum distributions, we measured the 3He(e, e′pp)n reaction, looking at events with high-momentum protons (pp>0.35 GeV/c) and a low-momentum neutron (pn<0.2 GeV/c). We examined two angular configurations: either both protons emitted forward or one proton emitted forward and one backward (with respect to the momentum transfer, q⃗). The measured relative momentum distribution of the events with one forward and one backward proton was much closer to the calculated initial-state pp relative momentum distribution, indicating that this is the preferred configuration for measuring SRC.
Phys. Rev. C. 06/2012; 85(6).
-
K. Park,
M. Guidal,
R. W. Gothe,
J. M. Laget,
M. Garçon,
K. P. Adhikari,
M. Aghasyan,
M. J. Amaryan,
M. Anghinolfi,
H. Avakian, [......],
E. Voutier,
N. K. Walford,
D. P. Watts,
L. B. Weinstein,
D. P. Weygand,
M. H. Wood,
N. Zachariou,
J. Zhang,
Z. W. Zhao,
I. Zonta
[show abstract]
[hide abstract]
ABSTRACT: The exclusive electroproduction of $\pi^+$ above the resonance region was
studied using the $\rm{CEBAF}$ Large Acceptance Spectrometer ($\rm{CLAS}$) at
Jefferson Laboratory by scattering a 6 GeV continuous electron beam off a
hydrogen target. The large acceptance and good resolution of $\rm{CLAS}$,
together with the high luminosity, allowed us to measure the cross section for
the $\gamma^* p \to n \pi^+$ process in 140 ($Q^2$, $x_B$, $t$) bins:
$0.16<x_B<0.58$, 1.6 GeV$^2<$$Q^2$$<4.5$ GeV$^2$ and 0.1 GeV$^2<$$-t$$<5.3$
GeV$^2$. For most bins, the statistical accuracy is on the order of a few
percent. Differential cross sections are compared to two theoretical models,
based either on hadronic (Regge phenomenology) or on partonic (handbag diagram)
degrees of freedom. Both can describe the gross features of the data reasonably
well, but differ strongly in their ingredients. If the handbag approach can be
validated in this kinematical region, our data contain the interesting
potential to experimentally access transversity Generalized Parton
Distributions.
06/2012;
-
The CLAS Collaboration,
Y. Ilieva,
B. L. Berman,
A. E. Kudryavtsev,
I. I. Strakovsky,
V. E. Tarasov,
M. Amarian,
P. Ambrozewicz,
M. Anghinolfi,
G. Asryan, [......],
L. B. Weinstein,
D. P. Weygand,
M. Williams,
E. Wolin,
M. H. Wood,
A. Yegneswaran,
L. Zana,
J. Zhang,
B. Zhao,
Z. Zhao
[show abstract]
[hide abstract]
ABSTRACT: High-quality cross sections for the reaction γd → π0
d have been measured using the CLAS at Jefferson Lab over a wide energy range near and above the η-meson photoproduction threshold. At backward c.m. angles for the outgoing pions, we observe a resonance-like structure near
E
γ = 700 MeV. Our model analysis shows that it can be explained by η excitation in the intermediate state. The effect is the result of the contribution of the N(1535)S
11-resonance to the amplitudes of the subprocesses occurring between the two nucleons and of a two-step process in which the
excitation of an intermediate η-meson dominates.
European Physical Journal A 04/2012; 43(3):261-267. · 2.19 Impact Factor
-
N Baillie,
S Tkachenko,
J Zhang,
P Bosted,
S Bültmann,
M E Christy,
H Fenker,
K A Griffioen,
C E Keppel,
S E Kuhn, [......],
W Tang,
M Ungaro,
M F Vineyard,
E Voutier,
D P Watts,
L B Weinstein,
D P Weygand,
M H Wood,
L Zana,
B Zhao
[show abstract]
[hide abstract]
ABSTRACT: We report on the first measurement of the F(2) structure function of the neutron from the semi-inclusive scattering of electrons from deuterium, with low-momentum protons detected in the backward hemisphere. Restricting the momentum of the spectator protons to ≲100 MeV/c and their angles to ≳100° relative to the momentum transfer allows an interpretation of the process in terms of scattering from nearly on-shell neutrons. The F(2)(n) data collected cover the nucleon-resonance and deep-inelastic regions over a wide range of Bjorken x for 0.65<Q(2)<4.52 GeV(2), with uncertainties from nuclear corrections estimated to be less than a few percent. These measurements provide the first determination of the neutron to proton structure function ratio F(2)(n)/F(2)(p) at 0.2≲x≲0.8 with little uncertainty due to nuclear effects.
Physical Review Letters 04/2012; 108(14):142001. · 7.37 Impact Factor
-
H. Egiyan,
J. Langheinrich,
R. W. Gothe,
L. Graham,
M. Holtrop,
H. Lu,
P. Mattione,
G. Mutchler,
K. Park,
E. S. Smith, [......],
D. J. Tedeschi,
M. Ungaro,
E. Voutier,
D. P. Watts,
L. B. Weinstein,
D. P. Weygand,
M. H. Wood,
N. Zachariou,
L. Zana,
B. Zhao
[show abstract]
[hide abstract]
ABSTRACT: We searched for the Φ−−(1860) pentaquark in the photoproduction process off the deuteron in the Ξ−π−-decay channel using CLAS. The invariant-mass spectrum of the Ξ−π− system does not indicate any statistically significant enhancement near the reported mass M=1.860 GeV. The statistical analysis of the sideband-subtracted mass spectrum yields a 90%-confidence-level upper limit of 0.7 nb for the photoproduction cross section of Φ−−(1860) with a consecutive decay into Ξ−π− in the photon-energy range 4.5 GeV<Eγ<5.5 GeV.
Phys. Rev. C. 01/2012; 85(1).
-
L. El Fassi,
L. Zana,
K. Hafidi,
M. Holtrop,
B. Mustapha,
W. K. Brooks,
H. Hakobyan,
X. Zheng,
K. P. Adhikari,
D. Adikaram, [......],
M. F. Vineyard,
H. Voskanyan,
E. Voutier,
D. Watts,
L. B. Weinstein,
D. P. Weygand,
M. H. Wood,
N. Zachariou,
B. Zhao,
Z. W. Zhao
[show abstract]
[hide abstract]
ABSTRACT: We have measured the nuclear transparency of the incoherent diffractive
$A(e,e'\rho^0)$ process in $^{12}$C and $^{56}$Fe targets relative to $^2$H
using a 5 GeV electron beam. The nuclear transparency, the ratio of the
produced $\rho^0$'s on a nucleus relative to deuterium, which is sensitive to
$\rho A$ interaction, was studied as function of the coherence length ($l_c$),
a lifetime of the hadronic fluctuation of the virtual photon, and the
four-momentum transfer squared ($Q^2$). While the transparency for both
$^{12}$C and $^{56}$Fe showed no $l_c$ dependence, a significant $Q^2$
dependence was measured, which is consistent with calculations that included
the color transparency effects.
01/2012;
-
N. Baillie,
S. Tkachenko,
J. Zhang,
P. Bosted,
S. Bultmann,
M. E. Christy,
H. Fenker,
K. A. Griffioen,
C. E. Keppel,
S. E. Kuhn, [......],
W. Tang,
M. Ungaro,
M. F. Vineyard,
E. Voutier,
D. P. Watts,
L. B. Weinstein,
D. P. Weygand,
M. H. Wood,
L. Zana,
B. Zhao
[show abstract]
[hide abstract]
ABSTRACT: We report on the first measurement of the F2 structure function of the
neutron from semi-inclusive scattering of electrons from deuterium, with
low-momentum protons detected in the backward hemisphere. Restricting the
momentum of the spectator protons to < 100 MeV and their angles to < 100
degrees relative to the momentum transfer allows an interpretation of the
process in terms of scattering from nearly on-shell neutrons. The F2n data
collected cover the nucleon resonance and deep-inelastic regions over a wide
range of Bjorken x for 0.65 < Q2 < 4.52 GeV2, with uncertainties from nuclear
corrections estimated to be less than a few percent. These measurements provide
the first determination of the neutron to proton structure function ratio
F2n/F2p at 0.2 < x < 0.8 with little uncertainty due to nuclear effects.
10/2011;
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M. Aghasyan,
H Avakian,
P Rossi,
E De Sanctis,
D. Hasch,
M Mirazita,
D. Adikaram,
M J Amaryan,
M Anghinolfi,
H Baghdasaryan, [......],
H. Voskanyan,
E. Voutier,
D. Watts,
L B Weinstein,
D P Weygand,
M H Wood,
L Zana,
J Zhang,
B Zhao,
Z W Zhao
[show abstract]
[hide abstract]
ABSTRACT: We present studies of single-spin asymmetries for neutral pion
electroproduction in semi-inclusive deep-inelastic scattering of 5.776 GeV
polarized electrons from an unpolarized hydrogen target, using the CEBAF Large
Acceptance Spectrometer (CLAS) at the Thomas Jefferson National Accelerator
Facility. A substantial $\sin \phi_h$ amplitude has been measured in the
distribution of the cross section asymmetry as a function of the azimuthal
angle $\phi_h$ of the produced neutral pion. The dependence of this amplitude
on Bjorken $x$ and on the pion transverse momentum is extracted with
significantly higher precision than previous data and is compared to model
calculations.
06/2011;
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R. Nasseripour,
B.L. Berman,
K.P. Adhikari,
D. Adikaram,
M. Anghinolfi,
J. Ball,
M. Battaglieri,
V. Batourine,
I. Bedlinskiy,
A.S. Biselli, [......],
M. Ungaro,
B. Vernarsky,
M.F. Vineyard,
E. Voutier,
D.P. Watts,
L.B. Weinstein,
D.P. Weygand,
M.H. Wood,
B. Zhao,
Z.W. Zhao
[show abstract]
[hide abstract]
ABSTRACT: We have measured the differential cross section for the γ3He→π+t reaction. This reaction was studied using the Continuous Electron Beam Accelerator Facility (CEBAF) Large Acceptance Spectrometer (CLAS) at Jefferson Lab. Real photons produced with the Hall-B bremsstrahlung tagging system in the energy range from 0.50 to 1.55 GeV were incident on a cryogenic liquid 3He target. The differential cross sections for the γ3He→π+t reaction were measured as a function of photon-beam energy and pion-scattering angle. Theoretical predictions to date cannot explain the large cross sections except at backward angles, showing that additional components must be added to the model.
Phys. Rev. C. 03/2011; 83(3).
-
H Avakian,
P Bosted,
V D Burkert,
L Elouadrhiri,
K P Adhikari,
M Aghasyan,
M Amaryan,
M Anghinolfi,
H Baghdasaryan,
J Ball, [......],
B Vernarsky,
M F Vineyard,
E Voutier,
D P Watts,
L B Weinstein,
D P Weygand,
M H Wood,
J Zhang,
B Zhao,
Z W Zhao
[show abstract]
[hide abstract]
ABSTRACT: We report the first measurement of the transverse momentum dependence of double-spin asymmetries in semi-inclusive production of pions in deep-inelastic scattering off the longitudinally polarized proton. Data have been obtained using a polarized electron beam of 5.7 GeV with the CLAS detector at the Jefferson Lab (JLab). Modulations of single spin asymmetries over the azimuthal angle between lepton scattering and hadron production planes ϕ have been measured over a wide kinematic range in Bjorken x and virtual photon squared four-momentum Q2. A significant nonzero sin2ϕ single spin asymmetry was observed for the first time indicating strong spin-orbit correlations for transversely polarized quarks in the longitudinally polarized proton.
Physical Review Letters 12/2010; 105(26):262002. · 7.37 Impact Factor
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X Qian,
W Chen,
H Gao,
K Hicks,
K Kramer,
J M Laget,
T Mibe,
Y. Qiang,
S Stepanyan,
D J Tedeschi, [......],
M F Vineyard,
E. Voutier,
L B Weinstein,
D P Weygand,
M H Wood,
N. Zachariou,
L Zana,
J Zhang,
B Zhao,
Z W Zhao
[show abstract]
[hide abstract]
ABSTRACT: We report the first measurement of the differential cross section on
$\phi$-meson photoproduction from deuterium near the production threshold for a
proton using the CLAS detector and a tagged-photon beam in Hall B at Jefferson
Lab. The measurement was carried out by a triple coincidence detection of a
proton, $K^+$ and $K^-$ near the theoretical production threshold of 1.57 GeV.
The extracted differential cross sections $\frac{d\sigma}{dt}$ for the initial
photon energy from 1.65-1.75 GeV are consistent with predictions based on a
quasifree mechanism. This experiment establishes a baseline for a future
experimental search for an exotic $\phi$-N bound state from heavier nuclear
targets utilizing subthreshold/near-threshold production of $\phi$ mesons.
11/2010;
-
H Baghdasaryan,
L B Weinstein,
J M Laget,
K P Adhikari,
M Aghasyan,
M Amarian,
M Anghinolfi,
H Avakian,
J Ball,
M Battaglieri, [......],
C E Taylor,
D J Tedeschi,
M Ungaro,
M F Vineyard,
E Voutier,
D P Watts,
D P Weygand,
M H Wood,
B Zhao,
Z W Zhao
[show abstract]
[hide abstract]
ABSTRACT: We have measured the 3He(e,e' pp)n reaction at an incident energy of 4.7 GeV over a wide kinematic range. We identified spectator correlated pp and pn nucleon pairs by using kinematic cuts and measured their relative and total momentum distributions. This is the first measurement of the ratio of pp to pn pairs as a function of pair total momentum p(tot). For pair relative momenta between 0.3 and 0.5 GeV/c, the ratio is very small at low p(tot) and rises to approximately 0.5 at large p(tot). This shows the dominance of tensor over central correlations at this relative momentum.
Physical Review Letters 11/2010; 105(22):222501. · 7.37 Impact Factor
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M H Wood,
R Nasseripour,
M Paolone, C Djalali,
D P Weygand,
K P Adhikari,
M Anghinolfi,
J Ball,
M Battaglieri,
V Batourine, [......],
S Tkachenko,
M Ungaro,
B Vernarsky,
M F Vineyard,
E Voutier,
D P Watts,
L B Weinstein,
J Zhang,
B Zhao,
Z W Zhao
[show abstract]
[hide abstract]
ABSTRACT: Because of their long lifetimes, the ω and ϕ mesons are the ideal candidates for the study of possible modifications of the in-medium meson-nucleon interaction through their absorption inside the nucleus. During the E01-112 experiment at the Thomas Jefferson National Accelerator Facility, the mesons were photoproduced from 2H, C, Ti, Fe, and Pb targets. This Letter reports the first measurement of the ratio of nuclear transparencies for the e+e- channel. The ratios indicate larger in-medium widths compared with what have been reported in other reaction channels. The absorption of the ω meson is stronger than that reported by the CBELSA-TAPS experiment and cannot be explained by recent theoretical models.
Physical Review Letters 09/2010; 105(11):112301. · 7.37 Impact Factor
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H Baghdasaryan,
L B Weinstein,
J M Laget,
K. P. Adhikari,
M. Aghasyan,
M Amarian,
M Anghinolfi,
H Avakian,
J Ball,
M Battaglieri, [......],
C. E. Taylor,
D J Tedeschi,
M Ungaro,
M F Vineyard,
E. Voutier,
D. P. Watts,
D P Weygand,
M H Wood,
B Zhao,
Z W Zhao
[show abstract]
[hide abstract]
ABSTRACT: We have measured the 3He(e,e'pp)n reaction at an incident energy of 4.7 GeV over a wide kinematic range. We identified spectator correlated pp and pn nucleon pairs using kinematic cuts and measured their relative and total momentum distributions. This is the first measurement of the ratio of pp to pn pairs as a function of pair total momentum, $p_{tot}$. For pair relative momenta between 0.3 and 0.5 GeV/c, the ratio is very small at low $p_{tot}$ and rises to approximately 0.5 at large $p_{tot}$. This shows the dominance of tensor over central correlations at this relative momentum. Comment: 4 pages, 4 figures, submitted to PRL
08/2010;
-
B. Dey,
C. A. Meyer,
M. Bellis,
M. E. McCracken,
M. Williams,
K. P. Adhikari,
M. Aghasyan,
M. Anghinolfi,
J. Ball,
M. Battaglieri, [......],
D. P. Watts,
B. Vernarsky,
M. F. Vineyard,
E. Voutier,
L. B. Weinstein,
M. H. Wood,
A. Yegneswaran,
J. Zhang,
B. Zhao,
Z. W. Zhao
[show abstract]
[hide abstract]
ABSTRACT: High-statistics measurements of differential cross sections and recoil polarizations for the reaction γp→K+Σ0 have been obtained using the CLAS detector at Jefferson Lab. We cover center-of-mass energies (√s) from 1.69 to 2.84 GeV, with an extensive coverage in the K+ production angle. Independent measurements were made using the K+pπ-(γ) and K+p(π-,γ) final-state topologies, and were found to exhibit good agreement. Our differential cross sections show good agreement with earlier CLAS, SAPHIR, and LEPS results, while offering better statistical precision and a 300-MeV increase in √s coverage. Above √s≈2.5 GeV, t- and u-channel Regge scaling behavior can be seen at forward and backward angles, respectively. Our recoil polarization (PΣ) measurements represent a substantial increase in kinematic coverage and enhanced precision over previous world data. At forward angles, we find that PΣ is of the same order of magnitude but opposite sign as PΛ, in agreement with the static SU(6) quark model prediction of PΣ≈-PΛ. This expectation is violated in some mid- and backward-angle kinematic regimes, where PΣ and PΛ are of similar magnitudes but also have the same signs. In conjunction with several other meson photoproduction results recently published by CLAS, the present data will help constrain the partial-wave analyses being performed to search for missing baryon resonances.
Phys. Rev. C. 08/2010; 82(2).
-
[show abstract]
[hide abstract]
ABSTRACT: Due to their long lifetimes, the $\omega$ and $\phi$ mesons are the ideal candidates for the study of possible modifications of the in-medium meson-nucleon interaction through their absorption inside the nucleus. During the E01-112 experiment at the Thomas Jefferson National Accelerator Facility, the mesons were photoproduced from $^{2}$H, C, Ti, Fe, and Pb targets. This paper reports the first measurement of the ratio of nuclear transparencies for the $e^{+}e^{-}$ channel. The ratios indicate larger in-medium widths compared with what have been reported in other reaction channels. Comment: 6 pages, 4 figures
06/2010;
