Measurements of dielectron production in collisions at , 39, and 62.4 GeV from the STAR experiment

Physical Review C

Angular distributions of charged particles relative to jet axes are studied in s N N= 200 GeV Au+ Au collisions as a function of the jet orientation with respect to the event plane. This differential study tests the expected path-length dependence of energy loss experienced by a hard-scattered parton as it traverses the hot and dense medium formed in heavy-ion collisions. A second-order event plane is used in the analysis as an experimental estimate of the reaction plane formed by the collision impact parameter and the beam direction. Charged-particle jets with 15< p T, jet< 20 and 20< p T, jet< 40 GeV/c were reconstructed with the anti-k T algorithm with radius parameter setting of R= 0.4 in the 20–50% centrality bin to maximize the initial-state eccentricity of the interaction region. The reaction plane fit method is implemented to remove the flow-modulated background with better precision than prior methods. Yields …

Physical Review X

The deconfined quark-gluon plasma (QGP) created in relativistic heavy-ion collisions enables the exploration of the fundamental properties of matter under extreme conditions. Noncentral collisions can produce strong magnetic fields on the order of 10 18 G, which offers a probe into the electrical conductivity of the QGP. In particular, quarks and antiquarks carry opposite charges and receive contrary electromagnetic forces that alter their momenta. This phenomenon can be manifested in the collective motion of final-state particles, specifically in the rapidity-odd directed flow, denoted as v 1 (y). Here, we present the charge-dependent measurements of d v 1/d y near midrapidities for π±, K±, and p (p) in Au+ Au and isobar (Ru 44 96+ Ru 44 96 and Zr 40 96+ Zr 40 96) collisions at s NN= 200 GeV, and in Au+ Au collisions at 27 GeV, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The combined …

Bulletin of the American Physical Society

Searches for permanent electric dipole moments (EDMs) in non-degenerate systems are sensitive probes of beyond-standard-model symmetry violation that could explain the dominance of matter over anti-matter. 225 Ra (t 1/2= 15 d, I= 1/2) is a particularly attractive system to use for an EDM measurement because its octupole-deformed nucleus, closely spaced nuclear ground-state parity doublet, and highly relativistic electrons make 225 Ra uniquely sensitive to symmetry-violating interactions in the nuclear medium. Previous measurements have limited the EDM of 225 Ra to less than 1.4× 10-23 e cm (95% CL). We report progress toward implementing several experimental upgrades that will enable measurements at the 10-26 e cm level. In particular, we report progress on laser cooling and trapping radium using the strong, dipole allowed 1 S 0 to 1 P 1 transition at 483 nm that will greatly increase the number of …

arXiv preprint arXiv:2404.13582

The production of light nuclei and hyper-nuclei in heavy-ion collisions, particularly at high baryon density, is crucial for understanding dynamical evolution of collision system and exploring the internal state of nuclear matter of compacted stellar. Despite being a topic of ongoing debate, an improved theoretical understanding is needed. In this work, production of light nuclei (, , He, He) and hyper-nuclei (H, H) was investigated using the JAM microscopic transport model combined with an afterburner coalescence process at 3 GeV Au+Au collisions. In the coalescence process, the formation of a specific nucleus is determined by its Wigner function. The calculated spectra, average , and rapidity distributions were compared with the measurements from the STAR experiment. We investigated the dynamic information carried by light nuclei, and determined the averaged spatial distance and momentum difference of constituent nucleons () for each nucleus species.

Physical Review X

The deconfined quark-gluon plasma (QGP) created in relativistic heavy-ion collisions enables the exploration of the fundamental properties of matter under extreme conditions. Noncentral collisions can produce strong magnetic fields on the order of 10 18 G, which offers a probe into the electrical conductivity of the QGP. In particular, quarks and antiquarks carry opposite charges and receive contrary electromagnetic forces that alter their momenta. This phenomenon can be manifested in the collective motion of final-state particles, specifically in the rapidity-odd directed flow, denoted as v 1 (y). Here, we present the charge-dependent measurements of d v 1/d y near midrapidities for π±, K±, and p (p) in Au+ Au and isobar (Ru 44 96+ Ru 44 96 and Zr 40 96+ Zr 40 96) collisions at s NN= 200 GeV, and in Au+ Au collisions at 27 GeV, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The combined …

The present invention provides a method for making a high strength, small grain size ceramic having a transgranular fracture mode by rapid densification of a green body and subsequent cooling of the densified ceramic. The ceramic may include dislocations, defects, dopants, and/or secondary phases that are formed as a result of the process and resulting in stress fields capable of redirecting or arresting cracks within the material. This ceramic can maintain transparency from ultraviolet to mid-wave infrared.

Physical Review D

The longitudinal and transverse spin transfers to Λ (Λ) hyperons in polarized proton-proton collisions are expected to be sensitive to the helicity and transversity distributions, respectively, of (anti) strange quarks in the proton, and to the corresponding polarized fragmentation functions. We report improved measurements of the longitudinal spin transfer coefficient, D L L, and the transverse spin transfer coefficient, D T T, to Λ and Λin polarized proton-proton collisions at s= 200 GeV by the STAR experiment at RHIC. The dataset includes longitudinally polarized proton-proton collisions with an integrated luminosity of 52 pb− 1, and transversely polarized proton-proton collisions with a similar integrated luminosity. Both datasets have about twice the statistics of previous results and cover a kinematic range of| η Λ (Λ)|< 1.2 and transverse momentum p T, Λ (Λ) up to 8 GeV/c. We also report the first measurements of the …

Physical Review X

The deconfined quark-gluon plasma (QGP) created in relativistic heavy-ion collisions enables the exploration of the fundamental properties of matter under extreme conditions. Noncentral collisions can produce strong magnetic fields on the order of 10 18 G, which offers a probe into the electrical conductivity of the QGP. In particular, quarks and antiquarks carry opposite charges and receive contrary electromagnetic forces that alter their momenta. This phenomenon can be manifested in the collective motion of final-state particles, specifically in the rapidity-odd directed flow, denoted as v 1 (y). Here, we present the charge-dependent measurements of d v 1/d y near midrapidities for π±, K±, and p (p) in Au+ Au and isobar (Ru 44 96+ Ru 44 96 and Zr 40 96+ Zr 40 96) collisions at s NN= 200 GeV, and in Au+ Au collisions at 27 GeV, recorded by the STAR detector at the Relativistic Heavy Ion Collider. The combined …

Physical Review C

We measure triangular flow relative to the reaction plane at 3 GeV center-of-mass energy in Au+ Au collisions at the BNL Relativistic Heavy Ion Collider. A significant v 3 signal for protons is observed, which increases for higher rapidity, higher transverse momentum, and more peripheral collisions. The triangular flow is essentially rapidity-odd with a slope at midrapidity, d v 3/d y|(y= 0), opposite in sign compared to the slope for directed flow. No significant v 3 signal is observed for charged pions and kaons. Comparisons with models suggest that a mean field potential is required to describe these results, and that the triangular shape of the participant nucleons is the result of stopping and nuclear geometry.

Bulletin of the American Physical Society

D12. 00002: Vector meson photoproduction and interference effects in Ultra Peripheral Collisions at STAR

Physical Review C

Two-particle Bose–Einstein momentum correlation functions are studied for charged-hadron pairs in lead-lead collisions at a center-of-mass energy per nucleon pair of s NN= 5.02 TeV. The data sample, containing 4.27× 10 9 minimum bias events corresponding to an integrated luminosity of 0.607 nb− 1, was collected by the CMS experiment in 2018. The experimental results are discussed in terms of a Lévy-type source distribution. The parameters of this distribution are extracted as functions of particle pair average transverse mass and collision centrality. These parameters include the Lévy index or shape parameter α, the Lévy scale parameter R, and the correlation strength parameter λ. The source shape, characterized by α, is found to be neither Cauchy nor Gaussian, implying the need for a full Lévy analysis. Similarly to what was previously found for systems characterized by Gaussian source radii, a …

Physical Review C

Angular distributions of charged particles relative to jet axes are studied in s N N= 200 GeV Au+ Au collisions as a function of the jet orientation with respect to the event plane. This differential study tests the expected path-length dependence of energy loss experienced by a hard-scattered parton as it traverses the hot and dense medium formed in heavy-ion collisions. A second-order event plane is used in the analysis as an experimental estimate of the reaction plane formed by the collision impact parameter and the beam direction. Charged-particle jets with 15< p T, jet< 20 and 20< p T, jet< 40 GeV/c were reconstructed with the anti-k T algorithm with radius parameter setting of R= 0.4 in the 20–50% centrality bin to maximize the initial-state eccentricity of the interaction region. The reaction plane fit method is implemented to remove the flow-modulated background with better precision than prior methods. Yields …

Physical Review D

The longitudinal and transverse spin transfers to Λ (Λ) hyperons in polarized proton-proton collisions are expected to be sensitive to the helicity and transversity distributions, respectively, of (anti) strange quarks in the proton, and to the corresponding polarized fragmentation functions. We report improved measurements of the longitudinal spin transfer coefficient, D L L, and the transverse spin transfer coefficient, D T T, to Λ and Λin polarized proton-proton collisions at s= 200 GeV by the STAR experiment at RHIC. The dataset includes longitudinally polarized proton-proton collisions with an integrated luminosity of 52 pb− 1, and transversely polarized proton-proton collisions with a similar integrated luminosity. Both datasets have about twice the statistics of previous results and cover a kinematic range of| η Λ (Λ)|< 1.2 and transverse momentum p T, Λ (Λ) up to 8 GeV/c. We also report the first measurements of the …

Physical Review C

Angular distributions of charged particles relative to jet axes are studied in s N N= 200 GeV Au+ Au collisions as a function of the jet orientation with respect to the event plane. This differential study tests the expected path-length dependence of energy loss experienced by a hard-scattered parton as it traverses the hot and dense medium formed in heavy-ion collisions. A second-order event plane is used in the analysis as an experimental estimate of the reaction plane formed by the collision impact parameter and the beam direction. Charged-particle jets with 15< p T, jet< 20 and 20< p T, jet< 40 GeV/c were reconstructed with the anti-k T algorithm with radius parameter setting of R= 0.4 in the 20–50% centrality bin to maximize the initial-state eccentricity of the interaction region. The reaction plane fit method is implemented to remove the flow-modulated background with better precision than prior methods. Yields …

Physical Review D

The longitudinal and transverse spin transfers to Λ (Λ) hyperons in polarized proton-proton collisions are expected to be sensitive to the helicity and transversity distributions, respectively, of (anti) strange quarks in the proton, and to the corresponding polarized fragmentation functions. We report improved measurements of the longitudinal spin transfer coefficient, D L L, and the transverse spin transfer coefficient, D T T, to Λ and Λin polarized proton-proton collisions at s= 200 GeV by the STAR experiment at RHIC. The dataset includes longitudinally polarized proton-proton collisions with an integrated luminosity of 52 pb− 1, and transversely polarized proton-proton collisions with a similar integrated luminosity. Both datasets have about twice the statistics of previous results and cover a kinematic range of| η Λ (Λ)|< 1.2 and transverse momentum p T, Λ (Λ) up to 8 GeV/c. We also report the first measurements of the …

Nuclear Science and Techniques

The energetic bremsstrahlung photons up to 100 MeV produced in heavy ion collisions can be used as a sensitive probe for short-range correlation in atomic nuclei. The energy of the -rays can be measured by collecting the Čerenkov light in the medium induced by the fast electrons generated in the Compton scattering or electromagnetic shower of the incident ray. Two types of detectors based on pure water and lead glass as sensitive materials were designed for this purpose. The response and optical photon propagation in the detectors were simulated based on electromagnetic and optical processes in Geant4. The inherent energy resolutions of for water and for lead glass were obtained. The geometry sizes of the lead glass and water were optimized to 30 cm  30 cm  30 cm and 60 cm  60 cm  120 cm, respectively, to detect high-energy -rays at 160 MeV. The …

arXiv preprint arXiv:2404.13582

The production of light nuclei and hyper-nuclei in heavy-ion collisions, particularly at high baryon density, is crucial for understanding dynamical evolution of collision system and exploring the internal state of nuclear matter of compacted stellar. Despite being a topic of ongoing debate, an improved theoretical understanding is needed. In this work, production of light nuclei (, , He, He) and hyper-nuclei (H, H) was investigated using the JAM microscopic transport model combined with an afterburner coalescence process at 3 GeV Au+Au collisions. In the coalescence process, the formation of a specific nucleus is determined by its Wigner function. The calculated spectra, average , and rapidity distributions were compared with the measurements from the STAR experiment. We investigated the dynamic information carried by light nuclei, and determined the averaged spatial distance and momentum difference of constituent nucleons () for each nucleus species.

A test of lepton flavor universality in and decays, as well as a measurement of differential and integrated branching fractions of a nonresonant decay are presented. The analysis is made possible by a dedicated data set of proton-proton collisions at 13 TeV recorded in 2018, by the CMS experiment at the LHC, using a special high-rate data stream designed for collecting about 10 billion unbiased b hadron decays. The ratio of the branching fractions to is determined from the measured double ratio of these decays to the respective branching fractions of the with and decays, which allow for significant cancellation of systematic uncertainties. The ratio is measured in the range 1.16.0 GeV , where is the invariant mass of the lepton pair, and is found to be 0.78, in agreement with the standard model expectation 1. This measurement is limited by the statistical precision of the electron channel. The integrated branching fraction in the same range, (12.420.68) 10, is consistent with the present world-average value and has a comparable precision.

A search for pair production of scalar and vector leptoquarks (LQs) each decaying to a muon and a bottom quark is performed using proton-proton collision data collected at 13 TeV with the CMS detector at the CERN LHC, corresponding to an integrated luminosity of 138 fb . No excess above standard model expectation is observed. Scalar (vector) LQs with masses less than 1810 (2120) GeV are excluded at 95% confidence level, assuming a 100% branching fraction of the LQ decaying to a muon and a bottom quark. These limits represent the most stringent to date.

Physics Letters B

We report results on an elastic cross section measurement in proton–proton collisions at a center-of-mass energy s= 510 GeV, obtained with the Roman Pot setup of the STAR experiment at the Relativistic Heavy Ion Collider (RHIC). The elastic differential cross section is measured in the four-momentum transfer squared range 0.23≤− t≤ 0.67 GeV 2. This is the only measurement of the proton-proton elastic cross section in this t range for collision energies above the Intersecting Storage Rings (ISR) and below the Large Hadron Collider (LHC) colliders. We find that a constant slope B does not fit the data in the aforementioned t range, and we obtain a much better fit using a second-order polynomial for B (t). This is the first measurement below the LHC energies for which the non-constant behavior B (t) is observed. The t dependence of B is determined using six subintervals of t in the STAR measured t range, and is in …

Physical Review C

The yrast and nonyrast states of Te 126 were populated in a fusion-evaporation reaction using a target of Sn 124 and α beam at 31 MeV energy. All the γ− γ coincidences were recorded using the Indian National Gamma Array at the Variable Energy Cyclotron Centre, India, and processed by a digital data-acquisition system. The level scheme was enriched with the addition of 65 new transitions and the identification of five new structures. Spin and parity assignments were made and the subsequent results were interpreted in the framework of the nuclear shell model using the large-scale shell-model code antoine.

Physical Review C

Collective behavior has been observed in high-energy heavy-ion collisions for several decades. Collectivity is driven by the high particle multiplicities that are produced in these collisions. At the CERN Large Hadron Collider (LHC), features of collectivity have also been seen in high-multiplicity proton-proton collisions that can attain particle multiplicities comparable to peripheral Pb-Pb collisions. One of the possible signatures of collective behavior is the decrease of femtoscopic radii extracted from pion and kaon pairs emitted from high-multiplicity collisions with increasing pair transverse momentum. This decrease can be described in terms of an approximate transverse mass scaling. In the present work, femtoscopic analyses are carried out by the ALICE Collaboration on charged pion and kaon pairs produced in p p collisions at s= 13 TeV from the LHC to study possible collectivity in p p collisions. The event-shape …

Physical Review C

Angular distributions of charged particles relative to jet axes are studied in s N N= 200 GeV Au+ Au collisions as a function of the jet orientation with respect to the event plane. This differential study tests the expected path-length dependence of energy loss experienced by a hard-scattered parton as it traverses the hot and dense medium formed in heavy-ion collisions. A second-order event plane is used in the analysis as an experimental estimate of the reaction plane formed by the collision impact parameter and the beam direction. Charged-particle jets with 15< p T, jet< 20 and 20< p T, jet< 40 GeV/c were reconstructed with the anti-k T algorithm with radius parameter setting of R= 0.4 in the 20–50% centrality bin to maximize the initial-state eccentricity of the interaction region. The reaction plane fit method is implemented to remove the flow-modulated background with better precision than prior methods. Yields …

Physical Review C

The first measurements of K*(892) 0 resonance production as a function of charged-particle multiplicity in Xe-Xe collisions at s N N= 5.44 TeV and p p collisions at s= 5.02 TeV using the ALICE detector are presented. The resonance is reconstructed at midrapidity (| y|< 0.5) using the hadronic decay channel K* 0→ K±π∓. Measurements of transverse-momentum integrated yield, mean transverse-momentum, nuclear modification factor of K* 0, and yield ratios of resonance to stable hadron (K* 0/K) are compared across different collision systems (p p, p-Pb, Xe-Xe, and Pb-Pb) at similar collision energies to investigate how the production of K* 0 resonances depends on the size of the system formed in these collisions. The hadronic rescattering effect is found to be independent of the size of colliding systems and mainly driven by the produced charged-particle multiplicity, which is a proxy of the volume of produced …

Physical Review C

The production of η and η′ mesons is studied in proton-proton and proton-lead collisions collected with the LHCb detector. Proton-proton collisions are studied at center-of-mass energies of 5.02 and 13 TeV and proton-lead collisions are studied at a center-of-mass energy per nucleon of 8.16 TeV. The studies are performed in center-of-mass (cm) rapidity regions 2.5< y c. m.< 3.5 (forward rapidity) and− 4.0< y c. m.<− 3.0 (backward rapidity) defined relative to the proton beam direction. The η and η′ production cross sections are measured differentially as a function of transverse momentum for 1.5< p T< 10 GeV and 3< p T< 10 GeV, respectively. The differential cross sections are used to calculate nuclear modification factors. The nuclear modification factors for η and η′ mesons agree at both forward and backward rapidity, showing no significant evidence of mass dependence. The differential cross sections of η …

Physical Review C

Erratum: Angular distribution of γ -rays from neutron-induced compound states of <SUP>140</SUP>La [Phys. Rev. C 97, 034622 (2018)] - NASA/ADS Now on home page ads icon ads Enable full ADS view NASA/ADS Erratum: Angular distribution of γ -rays from neutron-induced compound states of 140 La [Phys. Rev. C 97, 034622 (2018)] Okudaira, T. ; Takada, S. ; Hirota, K. ; Kimura, A. ; Kitaguchi, M. ; Koga, J. ; Nagamoto, K. ; Nakao, T. ; Okada, A. ; Sakai, K. ; Shimizu, HM ; Yamamoto, T. ; Yoshioka, T. Abstract Publication: Physical Review C Pub Date: February 2024 DOI: 10.1103/PhysRevC.109.029903 Bibcode: 2024PhRvC.109b9903O full text sources Publisher | © The SAO/NASA Astrophysics Data System adshelp[at]cfa.harvard.edu The ADS is operated by the Smithsonian Astrophysical Observatory under NASA Cooperative Agreement NNX16AC86A NASA logo Smithsonian logo Resources About ADS ADS …

Physical Review C

The measurement of the direct-photon spectrum from Au+ Au collisions at s N N= 200 GeV is presented by the PHENIX Collaboration using the external-photon-conversion technique for 0%–93% central collisions in a transverse-momentum (p T) range of 0.8–10 GeV/c. An excess of direct photons, above prompt-photon production from hard-scattering processes, is observed for p T< 6 GeV/c. Nonprompt direct photons are measured by subtracting the prompt component, which is estimated as N coll-scaled direct photons from p+ p collisions at 200 GeV, from the direct-photon spectrum. Results are obtained for 0.8< p T< 6.0 GeV/c and suggest that the spectrum has an increasing inverse slope from≈ 0.2 to 0.4 GeV/c with increasing p T, which indicates a possible sensitivity of the measurement to photons from earlier stages of the evolution of the collision. In addition, like the direct-photon production, the p T …

Physical Review C

Two-particle Bose–Einstein momentum correlation functions are studied for charged-hadron pairs in lead-lead collisions at a center-of-mass energy per nucleon pair of s NN= 5.02 TeV. The data sample, containing 4.27× 10 9 minimum bias events corresponding to an integrated luminosity of 0.607 nb− 1, was collected by the CMS experiment in 2018. The experimental results are discussed in terms of a Lévy-type source distribution. The parameters of this distribution are extracted as functions of particle pair average transverse mass and collision centrality. These parameters include the Lévy index or shape parameter α, the Lévy scale parameter R, and the correlation strength parameter λ. The source shape, characterized by α, is found to be neither Cauchy nor Gaussian, implying the need for a full Lévy analysis. Similarly to what was previously found for systems characterized by Gaussian source radii, a …

Physical Review C

The measurement of the direct-photon spectrum from Au+ Au collisions at s N N= 200 GeV is presented by the PHENIX Collaboration using the external-photon-conversion technique for 0%–93% central collisions in a transverse-momentum (p T) range of 0.8–10 GeV/c. An excess of direct photons, above prompt-photon production from hard-scattering processes, is observed for p T< 6 GeV/c. Nonprompt direct photons are measured by subtracting the prompt component, which is estimated as N coll-scaled direct photons from p+ p collisions at 200 GeV, from the direct-photon spectrum. Results are obtained for 0.8< p T< 6.0 GeV/c and suggest that the spectrum has an increasing inverse slope from≈ 0.2 to 0.4 GeV/c with increasing p T, which indicates a possible sensitivity of the measurement to photons from earlier stages of the evolution of the collision. In addition, like the direct-photon production, the p T …

Physical Review C

The production of K*(892)±meson resonance is measured at midrapidity (| y|< 0.5) in Pb− Pb collisions at s N N= 5.02 TeV using the ALICE detector at the CERN Large Hadron Collider. The resonance is reconstructed via its hadronic decay channel K*(892)±→ K S 0 π±. The transverse momentum distributions are obtained for various centrality intervals in the p T range of 0.4− 16 GeV/c. Measurements of integrated yields, mean transverse momenta, and particle yield ratios are reported and found to be consistent with previous ALICE measurements for K*(892) 0 within uncertainties. The p T-integrated yield ratio 2 K*(892)±/(K++ K−) in central Pb− Pb collisions shows a significant suppression at a level of 9.3 σ relative to p p collisions. Thermal model calculations result in an overprediction of the particle yield ratio. Although both hadron resonance gas in partial chemical equilibrium (HRG-PCE) and music+ smash …

Physical Review C

Utilizing rapidity-dependent measurements to map the QCD phase diagram provides a complementary approach to traditional beam-energy-dependent measurements around midrapidity. The changing nature of thermodynamic properties of QCD matter along the beam axis in heavy-ion collisions at low collision energies both motivates and poses challenges for this method. In this study, we derive the analytical cumulant-generating function for subsystems within distinct rapidity windows, while accounting for global net-baryon charge conservation of the full system. Rapidity-dependent net-baryon cumulants are then calculated for a system exhibiting inhomogeneity along the beam axis, and their sensitivity to finite acceptances through changing rapidity bin widths is explored. We highlight the nontrivial behaviors exhibited by these cumulants, underscoring their importance in establishing a noncritical baseline for …

Physical Review C

High spin states of K 40 populated through the Al 27 (F 19, α n p) K 40 reaction at 68 MeV beam energy were studied using the Indian National Gamma Array (INGA) facility. Six new levels and fourteen new transitions were added to the existing level scheme. The spins and parities of most of the levels were assigned, modified, or confirmed from R DCO, R ADO, and linear polarization measurements. The multipole mixing ratios (δ) for most of the transitions were measured. Large-basis shell-model calculations were performed to understand the microscopic origin of the levels. Different particle restrictions in s d and p f shell orbitals were used to explain the experimental results.

Physical Review C

The production of K*(892)±meson resonance is measured at midrapidity (| y|< 0.5) in Pb− Pb collisions at s N N= 5.02 TeV using the ALICE detector at the CERN Large Hadron Collider. The resonance is reconstructed via its hadronic decay channel K*(892)±→ K S 0 π±. The transverse momentum distributions are obtained for various centrality intervals in the p T range of 0.4− 16 GeV/c. Measurements of integrated yields, mean transverse momenta, and particle yield ratios are reported and found to be consistent with previous ALICE measurements for K*(892) 0 within uncertainties. The p T-integrated yield ratio 2 K*(892)±/(K++ K−) in central Pb− Pb collisions shows a significant suppression at a level of 9.3 σ relative to p p collisions. Thermal model calculations result in an overprediction of the particle yield ratio. Although both hadron resonance gas in partial chemical equilibrium (HRG-PCE) and music+ smash …

Physical Review C

Natural indium targets were exposed to high-energy bremsstrahlung radiation, from 9 MeV to 23 MeV. Using the measured γ spectra, the yield ratio of In 113 m and In 115 m was determined. It was checked to what extent the measured values of the yield ratio can be reproduced using the existing experimental data of cross sections of relevant photonuclear reactions, as well as cross sections obtained by talys calculations. The measured reaction yield ratio was used to reconstruct the energy differential cross section of In 115 (γ, 2 n) In 113 m using the unfolding procedure.

Physical Review C

Two-particle Bose–Einstein momentum correlation functions are studied for charged-hadron pairs in lead-lead collisions at a center-of-mass energy per nucleon pair of s NN= 5.02 TeV. The data sample, containing 4.27× 10 9 minimum bias events corresponding to an integrated luminosity of 0.607 nb− 1, was collected by the CMS experiment in 2018. The experimental results are discussed in terms of a Lévy-type source distribution. The parameters of this distribution are extracted as functions of particle pair average transverse mass and collision centrality. These parameters include the Lévy index or shape parameter α, the Lévy scale parameter R, and the correlation strength parameter λ. The source shape, characterized by α, is found to be neither Cauchy nor Gaussian, implying the need for a full Lévy analysis. Similarly to what was previously found for systems characterized by Gaussian source radii, a …

Physical Review C

Neutron transmission experiments can offer a new type of highly sensitive search for time-reversal invariance violating (TRIV) effects in nucleon-nucleon interactions via the same enhancement mechanism observed for large parity violating (PV) effects in neutron-induced compound nuclear processes. In these compound processes, the TRIV cross section is given as the product of the PV cross section, a spin factor κ, and a ratio of TRIV and PV matrix elements. We determined κ to be 0.59±0.05 for La 139+ n using both (n, γ) spectroscopy and (n ⃗+ 139 La ⃗) transmission. This result quantifies for the first time the high sensitivity of the La 139 0.75-eV p-wave resonance in a future search for effects of P-odd/T-odd interactions in (n ⃗+ 139 La ⃗) forward transmission.

Physical Review C

Two-particle Bose–Einstein momentum correlation functions are studied for charged-hadron pairs in lead-lead collisions at a center-of-mass energy per nucleon pair of s NN= 5.02 TeV. The data sample, containing 4.27× 10 9 minimum bias events corresponding to an integrated luminosity of 0.607 nb− 1, was collected by the CMS experiment in 2018. The experimental results are discussed in terms of a Lévy-type source distribution. The parameters of this distribution are extracted as functions of particle pair average transverse mass and collision centrality. These parameters include the Lévy index or shape parameter α, the Lévy scale parameter R, and the correlation strength parameter λ. The source shape, characterized by α, is found to be neither Cauchy nor Gaussian, implying the need for a full Lévy analysis. Similarly to what was previously found for systems characterized by Gaussian source radii, a …

Physical Review C

A measurement of the Mo 94 (p, γ) Tc 95 cross section was performed. The cross section was measured in the energy range E c. m.= 1.5–4.5 MeV, spanning essentially the entirety of the Gamow window relevant to the astrophysical γ process. The γ-summing technique was used to analyze the data. At lower energies the sum peak overlapped with peaks from the reaction F 19 (p, α γ) O 16, so a new analysis method was developed to filter out the contamination from the this reaction. The measured cross section values were compared to the non-smoker database. The measured cross sections show enhanced resonancelike features at low energies, which are not predicted in the non-smoker code. The effects of this new measurement on the reaction rate were examined. It was found that there is a significant enhancement at lower temperatures in the (p, γ) reaction rate due to the enhancements found in the cross …

Physical Review C

The complete and incomplete fusion cross sections for the Li 7+ Tl 205 reaction were measured at near barrier energies by the online characteristic γ-ray detection technique. The complete fusion (CF) cross sections at energies above the Coulomb barrier were found to be suppressed by∼ 26% compared to the coupled channel calculations. Reduced fusion cross sections for the present system at energies normalized to the Coulomb barrier were also found to be systematically lower than those with strongly bound projectiles forming a similar compound nucleus. The suppression observed in CF cross sections is found to be commensurate with the measured total incomplete fusion (ICF) cross sections. In the ICF cross sections, t-capture is found to be dominant than α-capture at all the measured energies. The systematic study of available CF, ICF, and total fusion data with the Li 7 projectile is performed.

Physical Review C

Project 8 has developed a novel technique, cyclotron radiation emission spectroscopy (CRES), for direct neutrino mass measurements. A CRES-based experiment on the beta spectrum of tritium has been carried out in a small-volume apparatus. We provide a detailed account of the experiment, focusing on systematic effects and analysis techniques. In a Bayesian (frequentist) analysis, we measure the tritium endpoint as 18 553− 19+ 18 (18 548− 19+ 19) eV and set upper limits of 155 (152) eV (90% CL) on the neutrino mass. No background events are observed beyond the endpoint in 82 days of running. We also demonstrate an energy resolution of 1.66±0.19 eV in a resolution-optimized magnetic trap configuration by measuring Kr 83 m 17.8-keV internal-conversion electrons. These measurements establish CRES as a low-background, high-resolution technique with the potential to advance neutrino mass …