1,760 research outputs found
Experimental activities in few-body physics
Understanding the few-nucleon system remains one of the challenges in modern
nuclear and hadron physics. Observables in few-nucleon scattering processes are
sensitive probes to study the two and many-body interactions between nucleons
in nuclei. In the past decades, several facilities provided a large data base
to study in detail the three-nucleon interactions below the pion-production
threshold by exploiting polarized proton and deuteron beams and
large-acceptance detectors. Only since recently, the four-nucleon scattering
process at intermediate energies has been explored. In addition, there is a
focus to collect data in the hyperon-nucleon sector, thereby providing access
to understand the more general baryon-baryon interaction. In this contribution,
some recent results in the few-nucleon sector are discussed together with some
of the preliminary results from a pioneering and exclusive study of the
four-nucleon scattering process. Furthermore, this paper discusses the
experimental activities in the hyperon sector, in particular, the perspectives
of the hyperon program of PANDA.Comment: 9 pages, 4 figures, proceedings of the 21st European Conference on
Few Body Problems in Physics, Salamanca, Spain, 30 August - 3 September 201
Studying the -mass in-medium in reactions
Simulations based on a coupled-channel transport model have been performed to
analyze the feasibility to study the in-medium mass exploiting the
process for C, Ca and Nb nuclei. The distortions due
to final-state interactions of the and background contributions from
the reaction are found to be small in the mass range
of interest ( GeV). Furthermore, the effect of the
detector resolution on the -mass determination is discussed
Measurement of Proton Electromagnetic Form Factors in e(+) e(-) -> p(p)over-bar in the Energy Region 2.00-3.08 GeV
The process of e+e-→pp̄ is studied at 22 center-of-mass energy points (s) from 2.00 to 3.08 GeV, exploiting 688.5 pb-1 of data collected with the BESIII detector operating at the BEPCII collider. The Born cross section (σpp̄) of e+e-→pp̄ is measured with the energy-scan technique and it is found to be consistent with previously published data, but with much improved accuracy. In addition, the electromagnetic form-factor ratio (|GE/GM|) and the value of the effective (|Geff|), electric (|GE|), and magnetic (|GM|) form factors are measured by studying the helicity angle of the proton at 16 center-of-mass energy points. |GE/GM| and |GM| are determined with high accuracy, providing uncertainties comparable to data in the spacelike region, and |GE| is measured for the first time. We reach unprecedented accuracy, and precision results in the timelike region provide information to improve our understanding of the proton inner structure and to test theoretical models which depend on nonperturbative quantum chromodynamics
Measurement of the branching fraction of the doubly Cabibbo-suppressed decay D0 →k+π-π0 and search for D0 →k+π-π0π0
Using 2.93 fb-1 of e+e- collision data collected at a center-of-mass energy of 3.773 GeV with the BESIII detector, we present a measurement of the branching fraction of the doubly Cabibbo-suppressed (DCS) decay D0→K+π-π0 and a search for the DCS decay D0→K+π-π0π0. The branching fraction of D0→K+π-π0 is determined to be [3.13-0.56+0.60(stat)±0.15(syst)]×10-4. No signal is observed for D0→K+π-π0π0, and an upper limit of 3.6×10-4 is set on the branching fraction at the 90% CL. We combine these results with the world-average branching fractions of their counterpart Cabibbo-favored decays to determine the ratios of the DCS over the Cabibbo-favored branching fractions, B(D0→K+π-π0)/B(D0→K-π+π0)=(0.22±0.04)% and B(D0→K+π-π0π0)/B(D0→K-π+π0π0)<br/
Dynamically generated and resonances in the hidden charm sector around 4.3 GeV
The interactions of -,
-, and related strangeness channels,
are studied within the framework of the coupled channel unitary approach with
the local hidden gauge formalism. A series of meson-baryon dynamically
generated relatively narrow and resonances are predicted
around 4.3 GeV in the hidden charm sector. We make estimates of production
cross sections of these predicted resonances in collisions for
PANDA at the forthcoming FAIR facility.Comment: 35 pages, 12 figure
Observation of psi (3686) -> n(n)over-bar and improved measurement of psi (3686) -> p(p)over-bar
We observe the decay psi (3686) -> n (n) over bar for the first time and measure psi (3686) -> p (p) over bar with improved accuracy by using 1.07 x 10(8) psi (3686) events collected with the BESIII detector. The measured branching fractions are B(psi(3686) -> n (n) over bar) = (3.06 +/- 0.06 +/- 0.14) x 10(-4) and B(psi(3686) -> p (p) over bar) = (3.05 +/- 0.02 +/- 0.12) x 10(-4). Here, the first uncertainties are statistical, and the second ones are systematic. With the hypothesis that the polar angular distributions of the neutron and proton in the center-of-mass system obey 1 + alpha cos(2) theta, we determine the a parameters to be alpha(n (n) over bar) = 0.68 +/- 0.12 +/- 0.11 and alpha(p (p) over bar) = 1.03 +/- 0.06 +/- 0.03 for psi(3686) -> n (n) over bar and psi(3686) -> p (p) over bar, respectively
Observation of the Singly Cabibbo-Suppressed Decay D+ -> omega pi(+) and Evidence for D-0 -> omega pi(0)
Based on 2.93 fb(-1) e(+)e(-) collision data taken at center-of-mass energy of 3.773 GeV by the BESIII detector, we report searches for the singly Cabibbo-suppressed decays D+ -> omega pi(+) and D-0 -> omega pi(0). A double tag technique is used to measure the absolute branching fractions B(D+ -> omega pi(+)) = (2.79 +/- 0.57 +/- 0.16) x 10(-4) and B(D-0 +/- omega pi(0)) = (1.17 +/- 0.34 +/- 0.07) x 10(-4), with statistical significances of 5.5 sigma and 4.1 sigma, where the first and second uncertainties are statistical and systematic, respectively
Proton-deuteron radiative capture cross sections at intermediate energies
Differential cross sections of the reaction have been
measured at deuteron laboratory energies of 110, 133 and 180 MeV. The data were
obtained with a coincidence setup measuring both the outgoing He and the
photon. The data are compared with modern calculations including all possible
meson-exchange currents and two- and three- nucleon forces in the potential.
The data clearly show a preference for one of the models, although the shape of
the angular distribution cannot be reproduced by any of the presented models.Comment: 6 pages, 6 figures, accepted for publication in EPJ
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