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Register a new userNuclear transparency effect of $pi^{-}$-mesons in p+$^{12}$C- and d+$^{12}$C- interactions at 4.2A GeV/c
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The use of nuclear transparency effect of pi^{-}-mesons in proton, and deuteron induced interactions with carbon nuclei at 4.2A GeV/c, to get information about the properties of nuclear matter, is presented in this work. Half angle (theta_{1/2}) technique is used to extract information on nuclear transparency effect. The theta_{1/2} divides the multiplicity of charged particles into two equal parts depending on their polar angle in the lab. frame in pp interactions. Particles with angle smaller than (incone particles) and greater than (outcone particles) theta_{1/2} are considered separate. The average values of multiplicity, momentum and transverse momentum of the pi^{-}-mesons are analyzed as a function of a number of identified protons in an event. We observed evidences in the data which could be considered as transparency effect. For quantitative analysis, the results are compared with cascade model. The observed effects are categorized into leading effect transparency and medium effect transparency. The transparency in the latter case could be the reason of collective interactions of grouped nucleons with the incident particles.
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The results of the measurements of the double-differential production cross-sections of pions in p-C and $pi^pm$-C interactions using the forward spectrometer of the HARP experiment are presented. The incident particles are 12 GeV/c protons and charged pions directed onto a carbon target with a thickness of 5% of a nuclear interaction length. For p-C interactions the analysis is performed using 100035 reconstructed secondary tracks, while the corresponding numbers of tracks for $pi^-$-C and $pi^+$-C analyses are 106534 and 10122 respectively. Cross-section results are presented in the kinematic range 0.5 GeV/c $leq p_{pi} <$ 8 GeV/c and 30 mrad $leq theta_{pi} <$ 240 mrad in the laboratory frame. The measured cross-sections have a direct impact on the precise calculation of atmospheric neutrino fluxes and on the improved reliability of extensive air shower simulations by reducing the uncertainties of hadronic interaction models in the low energy range.
We use an underground counting lab with an extremely low background to perform an activity measurement for the $^{12}$C+$^{13}$C system with energies down to $Erm_{c.m.}$=2.323 MeV, at which the $^{12}$C($^{13}$C,$p$)$^{24}$Na cross section is found to be 0.22(7) nb. The $^{12}$C+$^{13}$C fusion cross section is derived with a statistical model calibrated using experimental data. Our new result of the $^{12}$C+$^{13}$C fusion cross section is the first decisive evidence in the carbon isotope systems which rules out the existence of the astrophysical S-factor maximum predicted by the phenomenological hindrance model, while confirming the rising trend of the S-factor towards lower energies predicted by other models, such as CC-M3Y+Rep, DC-TDHF, KNS, SPP and ESW. After normalizing the model predictions with our data, a more reliable upper limit is established for the $^{12}$C+$^{12}$C fusion cross sections at stellar energies.
The recent search for non $q bar{q}$ mesons in $pi^{-}p$ interactions at Brookhaven National Laboratory is summarized. Many final states such as $eta pi$, $eta pi^{-}$, $a_{0} pi$, $f_{1} pi$, $a_{2} pi$, $b_{1} pi$, which are favored decay modes of exotics, are under investigation.
The neutron yield in $^{12}$C(d,n)$^{13}$N and the proton yield in $^{12}C(d,p)^{13}$C have been measured by deuteron beam from 0.6 MeV to 3 MeV which is delivered from a 4-MeV electro static accelerator bombarding on the thick carbon target. The neutrons are detected at $0degree$, $24degree$, $48degree$ and the protons at $135degree$ in the lab frame. The ratios of the neutron yield to the proton one have been calculated and can be used as an effective probe to pin down the resonances. The resonances are found at 1.4 MeV, 1.7 MeV, 2.5 MeV in $^{12}C(d,p)^{13}$C and at 1.6 MeV, 2.7 MeV in $^{12}$C(d,n)$^{13}$N. This method provides a way to reduce the systematic uncertainty and helps to confirm more resonances in compound nuclei.
Carbon and oxygen burning reactions, in particular, $^{12}$C+$^{12}$C fusion, are important for the understanding and interpretation of the late phases of stellar evolution as well as the ignition and nucleosynthesis in cataclysmic binary systems such as type Ia supernovae and x-ray superbursts. A new measurement of this reaction has been performed at the University of Notre Dame using particle-$gamma$ coincidence techniques with SAND (a silicon detector array) at the high-intensity 5U Pelletron accelerator. New results for $^{12}$C+$^{12}$C fusion at low energies relevant to nuclear astrophysics are reported. They show strong disagreement with a recent measurement using the indirect Trojan Horse method. The impact on the carbon burning process under astrophysical scenarios will be discussed.
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