Photoproduction of the f1(1285) meson Schumacher, R. A.; Adhikari, K. P.; Akbar, Z. ...
Physical review. C,
06/2016, Letnik:
93, Številka:
6
Journal Article
Recenzirano
Odprti dostop
The f1 (1285) meson with mass 1281.0 ± 0.8 MeV/c2 and width 18.4 ± 1.4 MeV (full width at half maximum) was measured for the first time in photoproduction from a proton target using CLAS at Jefferson ...Lab. Differential cross sections were obtained via the ηπ + π -, K+ K0 π -, and K-K0 π+ decay channels from threshold up to a center-of-mass energy of 2.8 GeV. The mass, width, and an amplitude analysis of the ηπ + π- final-state Dalitz distribution are consistent with the axial-vector JP = 1+ f1 (1285) identity, rather than the pseudoscalar 0-η (1295). The production mechanism is more consistent with s -channel decay of a high-mass N * state and not with t -channel meson exchange. Decays to η π π go dominantly via the intermediate a$^±_0$ (980) π ∓ states, with the branching ratio Γ a0π (no $\overline{K}K$) / Γ ηππ (all) = 0.74 ± 0.09 . The branching ratios Γ ($\overline{K}K$ π )/ Γ (ηππ) = 0.216 ± 0.033 and Γ (γρ0) / Γ (ηππ) = 0.047 ± 0.018 were also obtained. The first is in agreement with previous data for the f1 (1285), while the latter is lower than the world average.
Photoproduction of the f1(1285) meson Schumacher, R. A.; Adhikari, K. P.; Akbar, Z. ...
Physical review. C,
06/2016, Letnik:
93, Številka:
6
Journal Article
Recenzirano
The f(1)(1285) meson withmass 1281.0 +/- 0.8MeV/c(2) and width 18.4 +/- 1.4MeV (full width at half maximum) was measured for the first time in photoproduction from a proton target using CLAS at ...Jefferson Lab. Differential cross sections were obtained via the eta pi(+)pi(-), K+(K) over bar (0) pi(-), and (K-K0)pi(+) decay channels from threshold up to a center-of-mass energy of 2.8 GeV. The mass, width, and an amplitude analysis of the eta pi(+)pi(-) final-state Dalitz distribution are consistent with the axial-vector J(P) = 1(+) f(1)(1285) identity, rather than the pseudoscalar 0(-) eta(1295). The production mechanism is more consistent with s-channel decay of a high-mass N* state and not with t-channel meson exchange. Decays to eta pi pi go dominantly via the intermediate a(0)(+/-) (980)pi(-/+) states, with the branching ratio Gamma a(0)pi (no (K) over barK)/Gammaeta pi pi (all) = 0.74 +/- 0.09. The branching ratios Gamma (K (K) over bar pi)/Gamma(eta pi pi) = 0.216 +/- 0.033 and Gamma (gamma rho(0))/Gamma(eta pi pi) = 0.047 +/- 0.018 were also obtained. The first is in agreement with previous data for the f(1)(1285), while the latter is lower than the world average.
A photon beam test of the 4
m long prototype lead/scintillating-fibre module for the GlueX
electromagnetic barrel calorimeter was carried out in Hall B at the Thomas Jefferson National Accelerator ...Facility with the objective of measuring the energy and timing resolutions of the module as well as the number of photoelectrons generated. Data were collected over an energy range of 150–650
MeV at multiple positions and angles along the module. Details of the analysis at the centre of and perpendicular to the module are shown herein; the results are
σ
E
/
E
=
5.4
%
/
E
(
GeV
)
⊕
2.3
%
,
σ
Δ
T
/
2
=
70
/
E
ps, and 660 photoelectrons for 1
GeV at each end of the module.
High precision photon flux determination for photon tagging experiments Teymurazyan, A.; Ahmidouch, A.; Ambrozewicz, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
12/2014, Letnik:
767, Številka:
C
Journal Article
Recenzirano
The Jefferson Laboratory PrimEx Collaboration has developed and implemented a method to control the tagged photon flux in photoproduction experiments at the 1% level over the photon energy range from ...4.9 to 5.5GeV. This method has been successfully implemented in a high precision measurement of the neutral pion lifetime. Here, we outline the experimental equipment and the analysis techniques used to accomplish this. These include the use of a total absorption counter for absolute flux calibration, a pair spectrometer for online relative flux monitoring, and a new method for post-bremsstrahlung electron counting.
Introduction: Persons with preclinical Alzheimer’s disease (AD) show impairments in semantic and associative memory years before the onset of clinical symptoms. However, many tasks used to assess ...these deficits make use of previously learned stimuli, often within well-established semantic networks that may be more resistant to disease-related changes. No research has been conducted examining trained and derived relational responding (TDRR) in older adults or in the presence of AD risk factors. The purpose of this study was to determine whether a novel TDRR task would be sensitive to age-related and disease-risk cognitive changes. Method: Thirty younger adults and 15 older adults were tested on measures of processing speed, episodic memory, semantic memory, crystallized intelligence, and executive functioning. During the TDRR task, participants were taught two relations (e.g., figure-name) and asked to derive four other relations (e.g., name-house) based on prior learning. Participants were tested on each trained and derived relation. Accuracy rates and response time were obtained.Results: Overall, derived relations were identified as quickly and as accurately as trained relations. Older adults were slower and less accurate than younger adults. No differences existed between older family history + groups; however, younger adults with a family history of dementia were faster at correctly identifying relations than the family history negative group. Task performance correlated with measures of processing speed, crystallized intelligence, episodic memory, and semantic memory. Discussion: Older and younger adults were able to learn and derive novel relations quickly and accurately. Thus, the novel trained and derived relational responding task appears to be an easy, inexpensive test that may be sensitive to age-related cognitive changes and cognitive differences in young adults with a family history of dementia. In addition, this task provided an opportunity to examine the application of Relational Frame Theory, specifically trained and derived relational responding, as it applies to age- and disease-related cognitive changes. While future research is needed with a larger sample, this study offers promising preliminary results in identifying age-related and possibly disease risk-related cognitive changes.
Photoproduction of π0π0 and π0π± pairs from nuclei has been measured over a wide mass range (2H, 7Li, 12C, 40Ca, and natPb) for photon energies from threshold to 600 MeV. The experiments were ...performed at the MAMI accelerator in Mainz, using the Glasgow photon tagging spectrometer and a 4π electromagnetic calorimeter consisting of the Crystal Ball and TAPS detectors. A shift of the pion–pion invariant-mass spectra for heavy nuclei to small invariant masses has been observed for π0 pairs but also for the mixed-charge pairs. The precise results allow for the first time a model-independent analysis of the influence of pion final-state interactions. The corresponding effects are found to be large and must be carefully considered in the search for possible in-medium modifications of the σ-meson. Results from a transport model calculation reproduce the shape of the invariant-mass distributions for the mixed-charge pairs better than for the neutral pairs, but also for the latter differences between model results and experiment are not large, leaving not much room for σ-in-medium modification.
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