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The mass dependence of the transverse flow for $Z=1$--5 fragments from the collisions of $^{40}\mathrm{Ar}+^{27}\mathrm{Al}, ^{40}\mathrm{Ar}+^{48}\mathrm{Ti}$, and $^{40}\mathrm{Ar}+^{58}\mathrm{Ni}$ at 47 MeV/nucleon is investigated experimentally in this article. The transverse flow values are determined using the in-plane components of the fragment transverse momenta, where three conventional methods, i.e., the kinetic flow tensor method, the transverse momentum analysis method, and the azimuthal correlation method, are applied to reconstruct the reaction plane in an event-by-event basis. It is demonstrated from the comparison of the present experimental mass dependent flow measurements and the model simulations using an improved antisymmetrized molecular dynamics model that the experimentally observed abnormal $\ensuremath{\alpha}$ transverse flow enhancement is closely related to the reaction plane reconstruction procedure in the flow extraction. We further investigate the physical existence of the abnormal $\ensuremath{\alpha}$ flow behavior using a two-particle azimuthal correlation method, which allows us to provide the relative flow magnitude information with an identification of fragment charge number without the knowledge of the reaction plane differing from the three conventional methods. It is found that the relative flow magnitudes deduced from the two-particle azimuthal correlation functions with an identification of $Z$, with the correction for the recoil effect imposed by the momentum conservation, show a monotonically increasing trend as a function of fragment charge number, with no exception of the $\ensuremath{\alpha}$ flow enhancement. These results, in addition to those from the improved antisymmetrized molecular dynamics model simulations, definitely provide experimental evidences for the inexistence of the abnormal $\ensuremath{\alpha}$ flow behavior in the heavy-ion collisions at the present incident energy region in nature.

Reputation is a fundamental feature of human sociality as it sustains cooperative relationships among unrelated individuals. Research from various disciplines provides insights on how individuals form impressions of others, condition their behaviours based on the reputation of their interacting partners and spread or learn such reputations. However, past research has often neglected the socio-ecological conditions that can shape reputation systems and their effect on cooperation. Here, we outline how social environments, cultural values and institutions come to play a crucial role in how people navigate reputation systems. Moreover, we illustrate how these socio-ecological dimensions affect the interdependence underlying social interactions (e.g. potential recipients of reputational benefits, degree of dependence) and the extent to which reputation systems promote cooperation. To do so, we review the interdisciplinary literature that illustrates how reputation systems are shaped by the variation of prominent ecological features. Finally, we discuss the implications of a socio-ecological approach to the study of reputation and outline potential avenues for future research.This article is part of the theme issue ‘The language of cooperation: reputation and honest signalling’.

Albergo thermometers with double isotope, isotone, and isobar yield ratio pairs with one proton and/or neutron difference are investigated. Without any extra sequential decay correction, a real temperature value of $4.9\ifmmode\pm\else\textpm\fi{}0.5$ MeV is deduced from the yields of the experimentally reconstructed primary hot intermediate mass fragments (IMFs) from $^{64}\mathrm{Zn}+^{112}\mathrm{Sn}$ collisions at 40 MeV/nucleon using the Albergo thermometer for the first time. An experimental sequential decay correction from the apparent temperatures to the real ones for 12 other reaction systems with different neutron-proton ($N/Z$) asymmetries in the same experiment, $^{70}\mathrm{Zn}$, $^{64}\mathrm{Ni}$ on $^{112,124}\mathrm{Sn}$, $^{58,64}\mathrm{Ni}$, $^{197}\mathrm{Au}$, and $^{232}\mathrm{Th}$ at 40 MeV/nucleon, is performed using an empirical correction factor approach of Tsang et al. [Phys. Rev. Lett. 78, 3836 (1997)] with the deduced 4.9-MeV temperature value. The dependence of nuclear temperature on the source $N/Z$ asymmetry is further investigated using these deduced real source temperature values from the present 13 systems. It is found that the deduced real source temperatures at the present source $N/Z$ range show a rather weak dependence on the source $N/Z$ asymmetry. By comparison between our previous results and those from other independent experiments, a consistent description for the $N/Z$ asymmetry dependence of nuclear temperature is addressed.

Neutron-proton equilibration is a process which has been used to study the density dependence of the symmetry energy term in the nuclear equation-of-state. This study utilizes constrained molecular dynamics (CoMD) simulations of $^{70}\mathrm{Zn}\phantom{\rule{4pt}{0ex}}+\phantom{\rule{4pt}{0ex}}^{70}\mathrm{Zn}$ with collision energies of 35 and 45 MeV/nucleon. An algorithm is used which searches through CoMD events and identifies the PLF* after it separates from the target and determines its lifetime, $\mathrm{\ensuremath{\Delta}}t$. It also determines the fragments that the PLF* breaks apart into and determines their angular alignment. This technique gives an opportunity to explore how the average alignment of dynamically produced fragments, ${\ensuremath{\langle}\ensuremath{\alpha}\ensuremath{\rangle}}_{\mathrm{dyn}}$, evolves with PLF* lifetime. An approximately linear relationship was determined with $d{\ensuremath{\langle}\ensuremath{\alpha}\ensuremath{\rangle}}_{\mathrm{dyn}}/d\mathrm{\ensuremath{\Delta}}t=0.98\ifmmode\pm\else\textpm\fi{}0.08\phantom{\rule{0.16em}{0ex}}\mathrm{rad}/\mathrm{zs}$ and $1.06\ifmmode\pm\else\textpm\fi{}0.09\phantom{\rule{0.16em}{0ex}}\mathrm{rad}/\mathrm{zs}$ for the 35 and $45\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}/\mathrm{nucleon}$, respectively, indicating a correlation with magnitude consistent with classically determined values which were used for prior experimental studies.

We present a dedicated experimental setup that has been built in Institute of Physics of the Jagiellonian University and is currently used to search long lived super heavy elements (LLSHE) that could be produced in the reaction between heavy ions and then deposited in the active catcher (AC) scintillation material. The collisions between heavy nuclei $^{197}Au$ (7.5 A.MeV) and $^{232}Th$ have been performed during our experiment at the Cyclotron Institute, Texas A&M in 2015. An innovative apparatus, which consists of ΔE–E detectors, enables the registration and identification of spontaneous decays (α or fission - SF) of heavy products, which were deposited in the scintillation material of the AC. Unique feature of the apparatus is that the AC scintillators are at the same time ΔE part of each of ΔE–E detector. The other part, E part, is a silicon detector. This construction largely eliminates background events in the region where alpha particles emitted by decaying reaction products are expected. Our measurements should be sensitive to search for super heavy elements (SHE) which could be deposited in irradiated scintillators and which have lifetimes of a year till over a dozen of years. Some results of the continuous measurement that already lasts 1.5 year will be shown.

X. G. Cao, E. J. Kim, K. Hagel, M. Barbui, J. Gauthier, S. Wuenschel, G. Giuliani, M. R. D. Rodriguez, H. Zheng, M. Huang, A. Bonasera, R. Wada, N. Blando, G. Q. Zhang, C. Y. Wong A. Staszczak, Z. X. Ren, Y. K. Wang, S. Q. Zhang, J. Meng, J. B. Natowitz, Exclusive measurements for α and α conjugate exit channels are carried out for 35 MeV/nucleon 28Si induced reactions. Systematic analyses of these channels reveal high energy resonance structures in 7 de-excitation channels. The resonances are compared with results of several recent theoretical calculations for toroidal high-spin isomers. The possible underlying physics of these observations are discussed.

The Partial Truncated Icosahedron (ParTI) phoswich array has been designed for the detection of low energy charged pions and other light charged particles for the study of pionic fusion reactions. The array consists of 15 plastic/CsI(Tl) phoswich detector units arranged in approximately one hemisphere of a truncated icosahedron geometry. The phoswich detectors’ particle identification capabilities have been characterized. A pulse shape discrimination technique has demonstrated isotopic identification for Z = 1 and Z = 2 particles and elemental identification up to at least Z = 3. Utilization of digital electronics allows for increased sensitivity in event triggering and independent verification of pion detection. A calibration technique for the array has also been developed.

The traditional isoscaling technique has been used to analyze all isotopically identified particles from 70 Zn+ 70 Zn and 64 Zn+ 64 Zn collisions at 35 MeV/u. Two additional techniques, using an energy-averaged ratio and using the data present in the tail of energy spectra, are compared to the traditional method and show similar results. Isoscaling fit parameters α and β are found both globally and for each individual series of constant Z and N . The data are then split up between emitted fragments and projectile-like fragments. Isoscaling values for the two different types of fragments are shown to be different, emphasizing the importance of experimentally distinguishing between projectile-like fragments and emitted fragments in order to achieve accurate isoscaling parameters.

The dependence of the nuclear temperature on the source neutron-proton ($N/Z$) asymmetry has been experimentally investigated with the light charged particles (LCPs) generated from 13 reaction systems with different $N/Z$ asymmetries, $^{64}\mathrm{Zn}$ on $^{112}\mathrm{Sn}$, and $^{70}\mathrm{Zn}$, $^{64}\mathrm{Ni}$ on $^{112,124}\mathrm{Sn}$, $^{58,64}\mathrm{Ni}$, $^{197}\mathrm{Au}$, and $^{232}\mathrm{Th}$ at 40 MeV/u. A rather weak $N/Z$ asymmetry dependence of the source temperature has been qualitatively inferred from the extracted $N/Z$ asymmetry dependence of the apparent temperature and that of the relative temperature change by the sequential decay effects with the help of the theoretical simulations. Comparing the present result with those from our previous work and other available experimental results, a weak $N/Z$ asymmetry dependence of nuclear temperature is commonly observed in different independent experiments and with different thermometers, except for the result reported by McIntosh et al. [Phys. Lett. B 719, 337 (2013)]. The origin of the difference between the conclusion of the former group and that of McIntosh et al. is addressed, using statistical multifragmentation model (SMM) simulations.

Yields of equatorially emitted light isotopes, $1\le Z\le 14$, observed in ternary fission in the reaction $^{241}$Pu($n_{\rm th}$,f) are employed to determine apparent chemical equilibrium constants for low-temperature and low-density nuclear matter. The degree of liberation and role of medium modifications are probed through a comparison of experimentally derived reaction quotients with equilibrium constants calculated using a relativistic mean-field model employing a universal medium modification correction for the attractive $\sigma$ meson coupling. The results of these comparisons indicate that equilibrium is achieved for the lighter ternary fission isotopes. For the heavier isotopes experimental reaction quotients are well below calculated equilibrium constants. This is attributed to a dynamical limitation reflecting insufficient time for full equilibrium to develop. The role of medium effects leading to yield reductions is discussed as is the apparent enhancement of yields for $^8$He and other very neutron rich exotic nuclei., Comment: 8 pages, 2 figures

The dependence of the nuclear temperature on the source neutron-proton ($N/Z$) asymmetry is experimentally investigated with the intermediate mass fragments (IMFs) generated from thirteen reaction systems with different $N/Z$ asymmetries, $^{64}\mathrm{Zn}$ on $^{112}\mathrm{Sn}$ and $^{70}\mathrm{Zn}, ^{64}\mathrm{Ni}$ on $^{112,124}\mathrm{Sn}, ^{58,64}\mathrm{Ni}, ^{197}\mathrm{Au}, ^{232}\mathrm{Th}$ at 40 MeV/nucleon. The apparent source temperatures for these systems are determined from the measured IMF yields from the intermediate velocity sources using eight carbon-related double isotope ratio thermometers. A rather weak $N/Z$ asymmetry dependence of the source temperature is qualitatively inferred from the extracted $N/Z$ asymmetry dependence of the apparent temperature and that of the relative temperature change by the sequential decay effects with the help of the theoretical simulations. The present result is compared with those from other available experiments.

We study neutron-proton equilibration in dynamically deformed nuclear systems by investigating the correlations between the three largest fragments produced in collisions of $^{70}\mathrm{Zn}+^{70}\mathrm{Zn}$ at 35 MeV per nucleon. The rotation angle is interpreted as a measure of the duration of contact between the regions of the excited projectile-like fragment as it decays. In this work we address questions of whether there is a simultaneous or a double rupture scenario, sizing of the fragments, and alignment of the configuration.

The silicon telescopes of the Forward Array Using Silicon Technology (FAUST) have been recently upgraded with silicon detectors which use resistive charge-splitting to measure the position of charged particles. This is in addition to the measurement of the total energy that these charged particles deposit in the detector. The upgrade results in increased angular resolution with a much smaller number of signals than silicon strip detectors with similar resolution. A novel method of calibration has been used to demonstrate the efficacy of these position-sensitive detectors, and the detectors have been used in a commissioning experiment.

The dual-axis duo-lateral position-sensitive silicon detector was developed to detect charged particles with high quality position and energy resolution. When these detectors were used with conventional signal processing electronics, an empirically determined correction was used to improve energy resolution. In this work, the waveforms from the detector after preamplification are studied in detail to investigate position information contained in the waveforms. A 7.22 MeV/nucleon alpha particle beam was impinged directly on a masked dual-axis duo-lateral detector. Data obtained using a 228Th alpha particle source was also used. By studying the waveform characteristics that give rise to the position-dependent distortions, a new summed trigger analysis method has been developed to significantly improve linearity in position reconstruction without sacrificing energy resolution.

Alpha emitting radionuclides with medically relevant half-lives are interesting for treatment of tumors and other diseases because they deposit large amounts of energy close to the location of the radioisotope. Researchers at the Cyclotron Institute at Texas A&M University are developing a program to produce 211At, an alpha emitter with a medically relevant half-life. The properties of 211At make it a great candidate for targeted alpha therapy for cancer due to its short half-life (7.2 h). Astatine-211 has now been produced multiple times and reliability of this process is being improved.

The experimental liquid-gas phase transition signals are examined for the quasiprojectile (QP) reconstructed from the reactions of $^{40}\mathrm{Ar}+^{27}\mathrm{Al}$, $^{48}\mathrm{Ti}$, $^{58}\mathrm{Ni}$ at 47 MeV/nucleon, using measures of caloric curve, multiplicity derivative, moment parameters, and fluctuation of maximum fragment charge number (NVZ). The QP source is reconstructed, using moving source parametrizations on an event-by-event basis. For the determination of the temperature, a quadrupole fluctuation thermometer is used. Deuterons are chosen for the thermometer to minimize the Coulomb and secondary sequential decay effects. A new event-by-event method is proposed for the thermometer to determine the temperature. All measures show a characteristic signature around the temperature $T=9.0\ifmmode\pm\else\textpm\fi{}0.4$ MeV, which may suggest that the QP system goes into the liquid-gas phase transition at ${T}_{c}=8.3\ifmmode\pm\else\textpm\fi{}0.4$ MeV after the Coulomb correction.

The experimental excitation function for the $7\ensuremath{\alpha}$ de-excitation of $^{28}\mathrm{Si}$ nuclei excited to high excitation energies in the collisions of 35 MeV/nucleon $^{28}\mathrm{Si}$ with $^{12}\mathrm{C}$ reveals resonance structures. The possibility that these structures may indicate the population of toroidal high-spin isomers such as those predicted by a number of recent theoretical calculations is discussed and the need for further investigations is emphasized.

Accelerator-based Ion Beam Analysis (IBA) has been actively used at the Cyclotron Institute (CI) at Texas A&M University (TAMU) to support the undergraduate research program. PIXE (Particle Induced X-ray Emission) and PIGE (Particle Induced Gamma-ray Emission) are examples of traditional ion beam techniques for elemental analysis. In the past year, our laboratory has assembled PIXE and PIGE experiments with the intention of collaborating with other departments and universities in the study of contaminants’ pathways to the environment and characterization of materials and, in addition, contribute didactically to undergraduates involved in the project. The implementation of routine PIXE and PIGE analysis at the CI allows students to perform elemental composition studies nondestructively, for a large number of samples in a variety of matrices (environmental or biological) with minimal time and sample preparation. The experiments were performed at the TAMU CI, using the K150 cyclotron. Each matrix was bombarded with a proton beam that ranged from 3.6 - 6.3 MeV, with an intensity between 5 - 9 nA and a beam spot size of 5 - 10 mm. The resulting x- and gamma-rays were measured with SiPIN, SOO and CdTe high-performance x- and gamma-ray detectors, located at 45° and 135° with respect to the beam direction. We will discuss our recent projects in detail and the impact they have on the research program and on undergraduate education.Accelerator-based Ion Beam Analysis (IBA) has been actively used at the Cyclotron Institute (CI) at Texas A&M University (TAMU) to support the undergraduate research program. PIXE (Particle Induced X-ray Emission) and PIGE (Particle Induced Gamma-ray Emission) are examples of traditional ion beam techniques for elemental analysis. In the past year, our laboratory has assembled PIXE and PIGE experiments with the intention of collaborating with other departments and universities in the study of contaminants’ pathways to the environment and characterization of materials and, in addition, contribute didactically to undergraduates involved in the project. The implementation of routine PIXE and PIGE analysis at the CI allows students to perform elemental composition studies nondestructively, for a large number of samples in a variety of matrices (environmental or biological) with minimal time and sample preparation. The experiments were performed at the TAMU CI, using the K150 cyclotron. Each matrix was bombard...

We present a dedicated experimental setup which is currently used to search for long lived super heavy elements (SHE) implanted in catcher scintillators which were irradiated by reaction products of $^{197}$Au (7.5 A.MeV) projectile and $^{232}$Th target collisions during our experiment performed at Cyclotrone Institute, Texas A$\&$M University in 2015. The built-in novel measuring apparatus consists of $\Delta$E-E detector pairs which are able to register $\alpha$ or spontaneous fission (SF) decays of heavy reaction products deposited in the scintillators. Their unique feature is that the examined scintillators are at the same time $\Delta$E part of each of $\Delta$E-E detector while E part is a silicon detector. Our apparatus is dedicated to search for SHEs which have a lifetime of a year till tens of years. Results of commissioning tests of our setup are presented., Comment: 6 pages, 3 figures, presented at Zakopane Conference on Nulear Physics 2018, submitted to Acta Physica Polonica B

Identification of alpha cluster states analogous to the 12C Hoyle state in heavier alpha- conjugate nuclei can provide tests of the existence of alpha condensates in nuclei. Such states are predicted for 16O, 20Ne, 24Mg, 28Si etc. at excitation energies slightly above the multi-alpha particle decay threshold, but have not yet been experimentally identified. The Thick Target Inverse Kinematics (TTIK) technique can be used to study the breakup of excited self-conjugate nuclei into many alpha particles. The reaction 20Ne+{\alpha} was studied using a 20Ne beam at 12 MeV/nucleon from the K150 cyclotron at Texas A&M University. The TTIK method was used to study both single {\alpha}-particle emission and multiple {\alpha}-particle decays. Events with alpha multiplicity up to four were analyzed. The analysis of the three {\alpha} - particle emission data allowed the identification of the Hoyle state and other 12C excited states decaying into three alpha particles. The results are shown and compared with other data available in the literature. Although the statistics for events with alpha multiplicity four is low, the data show a structure at about 15.2 MeV that could indicate the existence in 16O of a state analogous to the 12C Hoyle state. This structure is confirmed by the re-analysis of alpha multiplicity four events from a previous experiment performed at 9.7 MeV/nucleon with a similar setup but lower granularity. Moreover, the reconstructed excitation energy of 24Mg for these events peaks at around 34 MeV, very close to the predicted excitation energy for an excited state analogous to the 12C Hoyle state in 24Mg., Comment: 22 pages, 16 figures

The production of $\ensuremath{\alpha}$-particle decaying heavy nuclei in reactions of 7.5--6.1 MeV/nucleon $^{238}\mathrm{U}$ +$^{232}\mathrm{Th}$ was explored using an in-beam detection array composed of YAP scintillators and gas ionization chamber-Si telescopes. Comparisons of $\ensuremath{\alpha}$ energies and half-lives for the observed products with those of the previously known isotopes and with theoretically predicted values indicate the observation of a number of previously unreported $\ensuremath{\alpha}$ emitters. $\ensuremath{\alpha}$-particle decay energies reaching as high as 12 MeV are observed. Many of these are expected to be from decay of previously unseen relatively neutron rich products. While the contributions of isomeric states require further exploration and specific isotope identifications need to be made, the production of heavy isotopes with quite high atomic numbers is suggested by the data.

One of the problems we are facing today is the energy consumption minimization, while maintaining the indoor thermal comfort in buildings. A potential solution to this issue is use of phase change materials (PCMs) in thermal energy storage (TES), where cold gets accumulated during the summer nights in order to reduce cooling load during the day. In winter, on the other hand, heat from solar air collector is stored for evening and morning hours when solar radiation is not available. The main objective of the paper is to examine experimentally whether it is possible to use such a storage unit for heating as well as for cooling. For this purpose 30 plates filled with paraffin (melting point around 22°C) were positioned into TES and applied with the same initial and boundary conditions as they are expected in reality. Experimental work covered flow visualization, measurements of air velocity in the channels between the plates, parametric analysis in conjunction with TES thermal response and measurements of the pressure drops. The results indicate that this type of storage technology could be advantageously used in real conditions. For optimized thermal behavior, only plate thickness should be reduced.

Resonance structures are observed in the excitation function of the 7α de-excitation of 28Si nuclei are observed in the collisions of 35 MeV/nucleon 28Si with 12C. These structures may indicate that toroidal high-spin isomers such as those predicted by recent theoretical calculations are populated.

The paper presents a novel instrumentation for rare events selection which was tested in our research of short lived super heavy elements production and detection. The instrumentation includes an active catcher multi elements system and dedicated electronics. The active catcher located in the forward hemisphere is composed of 63 scintillator detection modules. Reaction products of damped collisions between heavy ion projectiles and heavy target nuclei are implanted in the fast plastic scintillators of the active catcher modules. The acquisition system trigger delivered by logical branch of the electronics allows to record the reaction products which decay via the alpha particle emissions or spontaneous fission which take place between beam bursts. One microsecond wave form signal from FADCs contains information on heavy implanted nucleus as well as its decays., Comment: 12 pages, 5 figures, accepted for publication in Acta Physica Polonica B

Symmetry energy, temperature and density at the time of the intermediate mass fragment formation are determined in a self-consistent manner, using the experimentally reconstructed primary hot isotope yields and anti-symmetrized molecular dynamics (AMD) simulations. The yields of primary hot fragments are experimentally reconstructed for multifragmentation events in the reaction system Zn 64 + Sn 112 at 40 MeV / nucleon . Using the reconstructed hot isotope yields and an improved method, based on the modified Fisher model, symmetry energy values relative to the apparent temperature, a sym / T , are extracted. The extracted values are compared with those of the AMD simulations, extracted in the same way as those for the experiment, with the Gogny interaction with three different density-dependent symmetry energy terms. The a sym / T values change according to the density-dependent symmetry energy terms used. Using this relation, the density of the fragmenting system is extracted first. Then symmetry energy and apparent temperature are determined in a self consistent manner in the AMD model simulations. Comparing the calculated a sym / T values and those of the experimental values from the reconstructed yields, ρ / ρ 0 = 0.65 ± 0.02 , a sym = 23.1 ± 0.6 MeV and T = 5.0 ± 0.4 MeV are evaluated for the fragmenting system experimentally observed in the reaction studied.

The de-excitation of alpha-conjugate nuclei produced in reactions of 35 MeV/nucleon 40Ca with 40Ca has been investigated. Particular emphasis is placed on examining the dynamics of collisions leading to projectile-like fragment exit channels. A general exploration of the reaction systematics reveals the binary dissipative character of the collisions and a hierarchy effect similar to that seen for heavier systems. Investigation of the subset of events characterized by a total alpha-conjugate mass (alpha particles plus alpha-conjugate fragments) equal to 40 and atomic number equal to 20 reveals a dominance of alpha-conjugate exit channels. The hierarchy effect for these channels leads to the production of alpha-clustered neck structures with potentially exotic geometries and properties.

Neutron-proton equilibration was studied in dynamically-deformed nuclei produced in reactions $^{70}$Zn+$^{70}$Zn at 35A MeV. The composition of the two largest daughters of each excited projectile-like fragment is examined as a function of alignment angle. The lighter fragment is initially neutron rich relative to the heavier fragment, and the compositions evolve towards each other exponentially with increasing angle. The alignment angle, as a result of rotation, is related to time through the angular momentum of the projectile-like fragment, and a rate constant of 3 zs$^{-1}$ is extracted. This corresponds to a mean equilibration time of 0.3 zs. This technique provides a new window through which to gain insight into the nuclear equation of state.

We study neutron-proton equilibration in dynamically deformed nuclear systems by investigating the correlations between the two largest fragments produced in collisions of $^{70}\mathrm{Zn}+^{70}\mathrm{Zn}$, $^{64}\mathrm{Zn}+^{64}\mathrm{Zn}$, $^{64}\mathrm{Ni}+^{64}\mathrm{Ni}$ and $^{64}\mathrm{Zn}+^{64}\mathrm{Ni}$ at $35\phantom{\rule{4pt}{0ex}}\mathrm{MeV}$ per nucleon. The extent of equilibration is investigated using the rotation angle as a clock for the equilibration. The initially dissimilar fragments converge exponentially with consistent rate constants across a wide variety of reaction partners and systems, indicating that the equilibration follows first-order kinetics.

Ratios of differential chemical potential values relative to the temperature, $({\ensuremath{\mu}}_{n}\ensuremath{-}{\ensuremath{\mu}}_{p})/T$, extracted from isotope yields of 13 reaction systems at 40 MeV/nucleon are compared to those of a quantum statistical model to determine the temperature and symmetry energy values of the fragmenting system. The experimental $({\ensuremath{\mu}}_{n}\ensuremath{-}{\ensuremath{\mu}}_{p})/T$ values are extracted based on the modified Fisher model. Using the density value of $\ensuremath{\rho}/{\ensuremath{\rho}}_{0}=0.56$ from the previous analysis, the temperature and symmetry energy values of $T=4.6\ifmmode\pm\else\textpm\fi{}0.4$ MeV and ${a}_{\mathrm{sym}}=23.6\ifmmode\pm\else\textpm\fi{}2.1$ MeV are extracted in a framework of a quantum statistical model. These values agree well with those of the previous work, in which a self-consistent method was utilized with antisymmetrized molecular dynamics simulations. The extracted temperature and symmetry energies are discussed together with other experimental values published in literature.

Fermi energy heavy ion collisions provide a valuable tool to research nuclear reaction dynamics and the hot nuclear matter Equation of State (EOS) at sub/supra-normal densities. In this energy regime, multi-fragmentation becomes important and the ejected light particles and intermediate mass fragments (IMFs) with Z > 2 carry a great deal of information on the thermal and chemical evolution of the reaction system under investigation. Existing detectors [1] include those with excellent isotopic resolution with limited angular coverage or excellent geometric acceptance with moderate isotopic resolution. Much information has been extracted from experiments performed with these detectors [2–9]. Ideally, a detector array with both excellent isotopic resolution and with a nearly 4π angular coverage of discrete telescopes with a high granularity is desirable. NIMROD–ISiS at the Cyclotron Institute, TAMU, is designed for such purposes and provides a powerful detector array capable of both charged particle and neut...

The neutron detection efficiency of a DEMON detector, averaged over the whole volume, was calculated using GEANT and applied to determine neutron multiplicities in an intermediate heavy ion reaction. When a neutron source is set at a distance of about 1 m from the front surface of the detector, the average efficiency, eav , is found to be significantly lower (20-30%) than the efficiency measured at the center of the detector, e0 . In the GEANT simulation the ratio R= eav / e0 was calculated as a function of neutron energy. The experimental central efficiency multiplied by R was then used to determine the average efficiency. The results were applied to a study of the 64 Zn+ 112 Sn reaction at 40 A MeV which employed 16 DEMON detectors. The neutron multiplicity was extracted using a moving source fit. The derived multiplicities are compared well with those determined using the neutron ball in the NIMROD detector array in a separate experiment. Both are in good agreement with multiplicities predicted by a transport model calculation using an antisymmetric molecular dynamics (AMD) model code. © 2013 Elsevier B.V.

We study neutron-proton equilibration in dynamically deformed atomic nuclei created in nuclear collisions. The two ends of the elongated nucleus are initially dissimilar in composition and equilibrate on a subzeptosecond time scale following first-order kinetics. We use angular momentum to relate the breakup orientation to the time scale of the breakup. The extracted rate constant is 3 zs^{-1}, which corresponds to a mean equilibration time of 0.3 zs. This technique enables new insight into the nuclear equation of state that governs many nuclear and astrophysical phenomena leading to the origin of the chemical elements.

A basic feature of the nuclear equation of state is not yet understood: the dependence of the nuclear caloric curve on the neutron–proton asymmetry. Predictions of theoretical models differ on the magnitude and even the sign of this dependence. In this work, the nuclear caloric curve is examined for fully reconstructed quasi-projectiles around mass A = 50 . The caloric curve extracted with the momentum quadrupole fluctuation thermometer shows that the temperature varies linearly with quasi-projectile asymmetry N − Z A . An increase in asymmetry of 0.15 units corresponds to a decrease in temperature on the order of 1 MeV. These results also highlight the importance of a full quasi-projectile reconstruction in the study of thermodynamic properties of hot nuclei.

The BRAHMS collaboration has measured transverse momentum spectra of pions, kaons, protons, and antiprotons at rapidities 0 and 3 for Cu+Cu collisions at sNN=200 GeV. As the collisions become more central the collective radial flow increases while the temperature of kinetic freeze-out decreases. The temperature is lower and the radial flow weaker at forward rapidity. Pion and kaon yields with transverse momenta between 1.5 and 2.5 GeV/c are suppressed for central collisions relative to scaled p+p collisions. This suppression, which increases as the collisions become more central, is consistent with jet quenching models and is also present with comparable magnitude at forward rapidity. At such rapidities, initial state effects may also be present and persistence of the meson suppression to high rapidity may reflect a combination of jet quenching and nuclear shadowing. The ratio of protons to mesons increases as the collisions become more central and is largest at forward rapidities.

The multiplicity of fragments in Fermi energy heavy-ion collisions was experimentally extracted. Compared with the results of calculation using the antisymmetrized molecular dynamics (AMD) model which accounts for the primary fragments only, the results calculated using the AMD together with a statistical decay code GEMINI to account for the deexcitation of excited primary fragments are in better agreement with those extracted from the experiment. This observation indicates that the experimental multiplicity distribution may be significantly different from those of primary fragments.

Isoscaling is derived within a recently proposed modified Fisher model where the free energy near the critical point is described by the Landau O ( m 6 ) theory. In this model m = N f − Z f A f is the order parameter, a consequence of (one of) the symmetries of the nuclear Hamiltonian. Within this framework we show that isoscaling depends mainly on this order parameter through the ‘external (conjugate) field’ H. The external field is just given by the difference in chemical potentials of the neutrons and protons of the two sources. To distinguish from previously employed isoscaling relationships, this approach is dubbed: m-scaling. We discuss the relationship between this framework and the standard isoscaling formalism and point out some substantial differences in interpretation of experimental results which might result. These should be investigated further both theoretically and experimentally.

The experimental results reveal the isospin dependence of the nuclear phase transition in terms of the Landau Free Energy description of critical phenomena. Near the critical point, different ratios of the neutron to proton concentrations lead to different critical points for the phase transition which is analogous to the phase transitions in He 4- He 3 liquid mixtures. The antisymmetrized molecular dynamics (AMD) and GEMINI models calculations were also performed and the results will be discussed as well.

Invariant p T spectra and rapidity densities covering a large rapidity range ( − 0.1 y 3.5 ) are presented for π ± and K ± mesons from central Au + Au collisions at s NN = 62.4 GeV . The mid-rapidity yields of meson particles relative to their anti-particles are found to be close to unity ( π − / π + ∼ 1 , K − / K + ∼ 0.85 ) while the anti-proton to proton ratio is p ¯ / p ∼ 0.49 . The rapidity dependence of the π − / π + ratio is consistent with a small increase towards forward rapidities while the K − / K + and p ¯ / p ratios show a steep decrease to ∼0.3 for kaons and 0.022 for protons at y ∼ 3 . It is observed that the kaon production relative to its own anti-particle as well as to pion production in wide rapidity and energy ranges shows an apparent universal behavior consistent with the baryo-chemical potential, as deduced from the p ¯ / p ratio, being the driving parameter.

A very brief summary Of Our Current research on clustering in low density matter formed in near Fermi energy heavy ion collisions is presented. At the lowest densities and temperatures large alpha mass fractions are observed. Temperature and density dependent symmetry free energies have been derived from isoscaling analyzes of the yields of nuclei with A = 4. The symmetry free energies are far above those obtained in common effective interaction calculations, reflecting cluster formation, primarily of alpha particles, not included in such calculations.

The proton-to-pion ratios measured in the BRAHMS experiment for Au + Au and p + p collisions at s N N = 62.4 and 200 GeV are presented as a function of transverse momentum and collision centrality at selected pseudorapidities in the range of 0–3.8. A strong pseudorapidity dependence of these ratios is observed. We also compare the magnitude and p T -dependence of the p / π + ratios measured in Au + Au collisions at s N N = 200 GeV and η ≈ 2.2 with the same ratio measured at s N N = 62.4 GeV and η = 0 . The great similarity found between these ratios throughout the whole p T range (up to 2.2 GeV / c ) is consistent with particle ratios in A + A collisions being described with grand-canonical distributions characterized by the baryo-chemical potential μ B . At the collision energy of 62.4 GeV, we have observed a unique point in pseudorapidity, η = 3.2 , where the p / π + ratio is independent of the collision system size in a wide p T -range of 0.3 ⩽ p T ⩽ 1.8 GeV / c .

The BigSol Superconducting Solenoid Beam Line at the Texas A&M Superconducting Cyclotron has been used to measure energy losses of 40Ar, 84Kr, 197Au and 238U ions in mylar, aluminum and isobutane at energies ranging from the Bragg peak up to several MeV/nucleon. The experimental data are compared with predictions from the SRIM code. In general experimental data for 40Ar and 84Kr are in agreement with model predictions whereas differences on the order of 10% are evidenced in some cases for 197Au and 238U ions especially at and around the Bragg peak energies.