Search

In the quest to unravel the mysteries of the strong force and the underlying properties of the quark-gluon plasma, the ALICE collaboration at CERN has carried out a comprehensive study focusing on the correlations between net-conserved quantities such as net-baryon, net-charge and net-strangeness. These correlations play a crucial role in the study of QCD phase structure as they are closely related to the ratios of thermodynamic susceptibilities in lattice QCD calculations. This work mainly focuses on the correlations between net-kaon and net-proton, and net-kaon and net-charge in Pb$-$Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV using data recorded during LHC Run 2. The net-proton and net-kaon serve as proxies for net-baryon and net-strangeness, respectively, with measurements analyzed as a function of collision centrality. Theoretical predictions from the Thermal-FIST model are compared with experimental results, providing insights into the effects of resonance decays and charge conservation laws on the correlations., Comment: 4 pages, 2 figures; contribution to the 21st International Conference on Strangeness in Quark Matter (SQM-2024). arXiv admin note: text overlap with arXiv:2409.10939

The proton capture cross-section of the least abundant proton-rich stable isotope of cadmium, $^{108}$Cd (abundance 0.89\%), has been measured near the Gamow window corresponding to a temperature range of 3-4 GK. The measurement of the $^{108}$Cd(p,$\gamma$)$^{109}$In reaction was carried out using the activation technique. The cross-section at the lowest energy point of 3T$_9$, E$_p$$^{lab}$= 2.28 MeV, has been reported for the first time. The astrophysical S-factor was measured in the energy range relevant to the astrophysical p-process, between E$_p$$^{cm}$= 2.29 and 6.79 MeV. The experimental results have been compared with theoretical predictions of Hauser-Feshbach statistical model calculations using TALYS-1.96. A calculated proton-optical potential was implemented to achieve better fitting, with different combinations of available nuclear level densities (NLDs) and $\gamma$-ray strength functions in TALYS-1.96. The calculations provided satisfactory agreement with the experimental results. The reaction rate was calculated using the calculated potential in TALYS-1.96 and compared with the values provided in the REACLIB database.

The Zirconium (Z = 40) isotopic chain has attracted interest for more than four decades. The abrupt lowering of the energy of the first $2^+$ state and the increase in the transition strength B(E2; $2_1^\rightarrow 0_1^+$ going from $^{98}$Zr to $^{100}$Zr has been the first example of "quantum phase transition" in nuclear shapes, which has few equivalents in the nuclear chart. Although a multitude of experiments have been performed to measure nuclear properties related to nuclear shapes and collectivity in the region, none of the measured lifetimes were obtained using the Recoil Distance Doppler Shift method in the $\gamma\gamma$-coincidence mode where a gate on the direct feeding transition of the state of interest allows a strict control of systematical errors. This work reports the results of lifetime measurements for the first yrast excited states in $^{98-104}$Zr carried out to extract reduced transition probabilities. The new lifetime values in $\gamma\gamma$-coincidence and $\gamma$-single mode are compared with the results of former experiments. Recent predictions of the Interacting Boson Model with Configuration Mixing, the Symmetry Conserving Configuration Mixing model based on the Hartree-Fock-Bogoliubov approach and the Monte Carlo Shell Model are presented and compared with the experimental data.

Systematic study of theoretical estimation of nuclear cross section of charged particle induced reactions on rare earth nuclei has been carried out. The production cross section of the $^{150,149,148,146,144,143,141}$Pm and $^{149,147}$Nd nuclei were calculated theoretically via proton induced reaction on neodymium using TALYS (version 1.96) code in the default mode, with different combination of nuclear models as well as using adjusted nuclear model parameters from reaction threshold to the proton energy upto 65 MeV. The theoretically computed results were compared with the experimental results taken from EXFOR database and literature, reported by various research groups. Moreover, the effect of the various Level Density Models (LDMs), Preequilibrium Models (PEs), Optical Model Potentials (OMPs), gamma Strength Functions ($\gamma$SFs) in the cross section calculation were taken into consideration. The present theoretical analysis will help to understand the theory of nuclear reaction models and improve the evaluated nuclear data libraries., Comment: 15 pages, 13 figures, to be published in Chinese Physics C

To explore the quantum chromodynamics (QCD) phase transitions and the properties of quark$-$gluon plasma, the ALICE collaboration at CERN has conducted an extensive analysis of the correlations among net-conserved quantities, namely net-baryon, net-charge, and net-strangeness. These correlations are essential for understanding the QCD phase structure, as they are directly connected to ratios of thermodynamic susceptibilities calculated in lattice QCD. This analysis focuses on the correlations between net-kaon and net-proton, as well as net-kaon and net-charge, in Pb$-$Pb collisions at $\sqrt{s_\mathrm{NN}} = 5.02$ TeV, where net-proton and net-kaon serve as effective proxies for net-baryon and net-strangeness, respectively. A comparison with theoretical predictions from the Thermal-FIST model sheds light on the role of resonance decays and the effects of charge conservation laws in shaping these correlations. Furthermore, the measurements show sensitivity to the correlation volume in which these conservation laws are applied, underscoring the importance of modeling the underlying dynamics to fully understand the experimental results on fluctuations and correlations in heavy-ion collisions., Comment: 6 pages, 4 figures; contribution to the 42nd International Conference on High Energy physics (ICHEP-2024)

This work presents the first calibration experiment of a 3 MV Tandetron accelerator, FRENA, performed in May 2022. The $^7$Li(p,n) reaction threshold was measured to calibrate the terminal voltage measuring device. A LiF target of thickness 175 $\mu$g/cm$^2$ was used in the experiment. The measured threshold was 1872$\pm$2.7 keV, indicating 6$-$10 keV energy shift.

The measurement of the $^7$Be($d$,$^3$He)$^6$Li* transfer cross section at 5 MeV/u is carried out. The population of the 2.186 MeV excited state of $^6$Li in this reaction channel is observed for the first time. The experimental angular distributions have been analyzed in the finite range DWBA and coupled-channel frameworks. The effect of the $^7$Be($d$,$^3$He)$^6$Li reaction on both the $^6$Li and $^7$Li abundances are investigated at the relevant big-bang nucleosynthesis energies. The excitation function is calculated by TALYS and normalized to the experimental data. The $S$ factor of the ($d$,$^3$He) channel from the present work is about 50$\%$ lower than existing data at nearby energies. At big-bang energies, the $S$ factor is about three orders of magnitude smaller than that of the ($d,p$) channel. The ($d$,$^3$He) reaction rate is found to have a less than 0.1$\%$ effect on the $^{6,7}$Li abundances., Comment: 7 pages, 5 figures

The detailed process of preparing enriched $^{108}$Cd targets on mylar and copper backing using the vacuum evaporation technique is described. These targets were employed in an experiment to measure the proton capture cross-section at energies significantly below the Coulomb barrier, for the astrophysical p-process studies. Due to the low melting point and high vapor pressure of cadmium, some adjustments were implemented in the Telemark multipocket e-beam setup. The target thickness was determined through the measurement of alpha particle energy loss from a triple alpha source and also by RBS measurements. The thickness of the $^{108}$Cd films varies between 290 to 660 $\mu$g/cm$^2$, with a non-uniformity of approximately 10$\%$. X-ray Photoelectron Spectroscopy (XPS) and X-ray Fluorescence (XRF) analyses were conducted to examine the presence of impurities and to assess surface morphology, phase, and chemical composition.

Neutron deficient nuclei from $^{74}$Se$-^{196}$Hg are thought to be produced by $\gamma$-induced reactions ($\gamma$,n), ($\gamma$,p) and ($\gamma,\alpha$) processes. The relatively high abundance of $^{113}$In odd A $p$-nuclei has inspired to study its production processes. As reaction with $\gamma$-beam is difficult to perform in the laboratory, $\gamma$-induced reaction rate is calculated from the inverse reaction data employing reciprocity theorem. Stacked foil activation method was used to measure the $^{113}$In($\alpha,\gamma$) and $^{113}$In($\alpha$, n) reactions cross-section near the astrophysical energies. Theoretical statistical model calculations were performed with different nuclear input parameters and compared with the experimental results. An appropriate $\alpha$-optical potential has been identified from the ($\alpha,\gamma$) and ($\alpha$, n) fitting, which provides the major source of uncertainty in the statistical model calculations. The other nuclear input parameters like level density, and $\gamma$-ray strength function were also constrained for theoretical calculations. $^{113}$In($\alpha,\gamma$)$^{117}$Sb and $^{117}$Sb($\alpha,\gamma$)$^{113}$In reaction rates were calculated using best-fitted input parameters.

The cross-section measurement of $^{144}$Sm(p, $\gamma$)$^{145}$Eu (T$_{1/2}=$5.93(4) days) reaction has been performed at proton energies around 2.6, 3.1, 3.7, 4.1, 4.2, 4.7, 5.1, 5.5, 5.9, 6.4, 6.8 MeV using the activation technique. These energies correspond to the Gamow window for 3, 4 GK and a partial portion for 2 GK. $^{144}$Sm has been chosen for the present study because of its significantly higher abundance compared to the other neighboring $p$-nuclides (Z $>$ 50). The astrophysical $S-$factor of this reaction has been measured for the first time at E$^{cm}_p=$ 2.57$\pm$0.13 MeV, $S-$ factor$=$2.542$\pm$1.152($\times$10$^{10}$) MeV-b. Cross-section data were compared with the previously measured experimental data from literature and the theoretical predictions obtained using Hauser-Feshbach statistical model codes TALYS 1.96 and NON-SMOKER. A satisfactory agreement between experimental data and theoretical results was observed. Molecular deposition technique was used to prepare the $^{144}$Sm targets having thickness between 100$-$350 $\mu$g/cm$^2$ on Al backing. Obtained results were utilized to predict the reaction rates for $^{144}$Sm (p, $\gamma$) and $^{145}$Eu ($\gamma$, p) reactions using TALYS 1.96 and the reciprocity theorem.

Theoretical considerations suggest an ordering of the ratios of net-baryon number fluctuations in the vicinity of the transition from the low-temperature hadronic phase to the high temperature quark-gluon plasma phase at small values of the baryon chemical potential, $\mu_B$, in the QCD phase diagram. The ordering hierarchy is $\frac{\chi_6}{\chi_2} < \frac{\chi_5}{\chi_1} < \frac{\chi_4}{\chi_2} < \frac{\chi_3}{\chi_1}$, where $\chi_n$ is the $n^\mathrm{th}$ order cumulant of net-baryon number fluctuation. The STAR experiment observed this hierarchy in the ordering of cumulant ratios of net-proton number (a proxy of net-baryon number) for a range of colliding energies. These inequalities can be tested in spin models by taking the corresponding order parameters in the model as an analog of baryon density. We employed two different models: the two-state and three-state Potts models in two dimensions, which undergo a transition from an ordered phase to a disordered phase at their respective critical temperature. Simulations were performed on square lattices of different sizes using the Wolff algorithm. The cumulants of total magnetization are obtained up to the sixth order in both of these models in a temperature range near their corresponding critical temperatures. With increasing lattice size, height (trough) of the peaks (dips) of the higher-order cumulants appears to increase with the increase in the order of the cumulants. Except in a narrow range above the critical temperature of the three-state Potts model, the complete inequality or its complete reverse is not satisfied in the temperature ranges simulated.

{\beta} decay of neutron-rich isotopes 43,45 S,studied at the National Superconducting Cyclotron Laboratory is reported here. {\beta} delayed {\gamma} transitions were detected by an array of 16 clover detectors surrounding the Beta Counting Station which consists of a 40x40 Double Sided Silicon Strip Detector followed by a Single Sided Silicon Strip Detector. {\beta} decay half-lives have been extracted for 43,45 S by correlating implants and decays in the pixelated implant detector with further coincidence with {\gamma} transitions in the daughter nucleus. The level structure of 43,45 Cl is expanded by the addition of 20 new {\gamma} transitions in 43Cl and 8 in 45 Cl with the observation of core excited negative-parity states for the first time. For 45 S decay, a large fraction of the {\beta} decay strength goes to delayed neutron emission populating states in 44 Cl which are also presented. Comparison of experimental observations is made to detailed shell-model calculations using the SDPFSDG-MU interaction to highlight the role of the diminished N = 28 neutron shell gap and the near degeneracy of the proton s 1/2 and d 3/2 orbitals on the structure of the neutron-rich Cl isotopes. The current work also provides further support to a ground state spin-parity assignment of 3/2 + in 45 Cl.

Results from the study of $\beta^-$-decay of $^{45}$Cl, produced in the fragmentation of a 140-MeV/u $^{48}$Ca beam, are presented. The half-life for $^{45}$Cl $\beta$-decay is measured to be 513(36) ms. The $\beta^-$ and $\beta^- 1n$ decay of $^{45}$Cl populated excited states in $^{45,44}$Ar, respectively. On the basis of $\gamma$-ray singles and $\gamma$-$\gamma$ coincidence data, decay schemes for the two daughter nuclei have been established. They are compared with shell model calculations using the FSU interaction. The low-lying negative parity states for $^{45}$Ar are well described by a single particle (neutron) occupying orbitals near the Fermi surface, whereas neutron excitations across the $N = 20$ shell gap are needed to explain the positive-parity states which are expected to be populated in allowed Gamow-Teller $\beta$-decay of $^{45}$Cl. The highest $\beta$-feeding to the 5/2$^+$ state in $^{45}$Ar from the ground state of $^{45}$Cl points towards a 3/2$^+$ spin-parity assignment of the ground state of the parent over the other possibility of 1/2$^+$. The high Q$_{\beta^-}$ value of $^{45}$Cl decay allows for the population of $1p1h$ states above the neutron separation energy in $^{45}$Ar leading to positive parity states of $^{44}$Ar being populated by removal of one neutron from the $sd$ shell. The spin-parities of the excited levels in $^{44}$Ar are tentatively assigned for the first time by comparison with the shell model calculations. The 2978~keV level of $^{44}$Ar is identified as the excited 0$^+$ level which could correspond to a different configuration from the ground state., Comment: 11 pages, 10 figures

This White Paper presents the community inputs and scientific conclusions from the Hot and Cold QCD Town Meeting that took place September 23-25, 2022 at MIT, as part of the Nuclear Science Advisory Committee (NSAC) 2023 Long Range Planning process. A total of 424 physicists registered for the meeting. The meeting highlighted progress in Quantum Chromodynamics (QCD) nuclear physics since the 2015 LRP (LRP15) and identified key questions and plausible paths to obtaining answers to those questions, defining priorities for our research over the coming decade. In defining the priority of outstanding physics opportunities for the future, both prospects for the short (~ 5 years) and longer term (5-10 years and beyond) are identified together with the facilities, personnel and other resources needed to maximize the discovery potential and maintain United States leadership in QCD physics worldwide. This White Paper is organized as follows: In the Executive Summary, we detail the Recommendations and Initiatives that were presented and discussed at the Town Meeting, and their supporting rationales. Section 2 highlights major progress and accomplishments of the past seven years. It is followed, in Section 3, by an overview of the physics opportunities for the immediate future, and in relation with the next QCD frontier: the EIC. Section 4 provides an overview of the physics motivations and goals associated with the EIC. Section 5 is devoted to the workforce development and support of diversity, equity and inclusion. This is followed by a dedicated section on computing in Section 6. Section 7 describes the national need for nuclear data science and the relevance to QCD research., Comment: QCD Town Meeting White Paper, as submitted to 2023 NSAC LRP committee on Feb. 28, 2023

We present local, position-space chiral NN potentials through four orders of chiral effective field theory ranging from leading order (LO) to next-to-next-to-next-to-leading order (N3LO, fourth order) of the Delta-less version of the theory. The long-range parts of these potentials are fixed by the very accurate pi-N LECs as determined in the Roy-Steiner equations analysis. At the highest order (N3LO), the NN data below 190 MeV laboratory energy are reproduced with the respectable chi^2/datum of 1.45. A comparison of the N3LO potential with the phenomenological Argonne v_18 (AV18) potential reveals substantial agreement between the two potentials in the intermediate range ruled by chiral symmetry, thus, providing a chiral underpinning for the phenomenological AV18 potential. Our chiral NN potentials may serve as a solid basis for systematic ab initio calculations of nuclear structure and reactions that allow for a comprehensive error analysis. In particular, the order by order development of the potentials will make possible a reliable determination of the truncation error at each order. Our new family of local position-space potentials differs from existing potentials of this kind by a weaker tensor force as reflected in relatively low D-state probabilities of the deuteron (P_D less or equal 4.0% for our N3LO potentials) and predictions for the triton binding energy above 8.00 MeV (from two-body forces alone). As a consequence, our potentials may lead to different predictions when applied to light and intermediate-mass nuclei in ab initio calculations and, potentially, help solve some of the outstanding problems in microscopic nuclear structure., Comment: 36 pages, 14 figures. arXiv admin note: text overlap with arXiv:1703.05454. More discussion on contacts and Fierz reordering

The elastic and inelastic scattering of $^7$Be from $^{12}$C have been measured at an incident energy of 35 MeV. The inelastic scattering leading to the 4.439 MeV excited state of $^{12}$C has been measured for the first time. The experimental data cover an angular range of $\theta_{cm}$ = 15$^{\circ}$-120$^{\circ}$. Optical model analyses were carried out with Woods-Saxon and double-folding potential using the density dependent M3Y (DDM3Y) effective interaction. The microscopic analysis of the elastic data indicates breakup channel coupling effect. A coupled-channel analysis of the inelastic scattering, based on collective form factors, show that mutual excitation of both $^7$Be and $^{12}$C is significantly smaller than the single excitation of $^{12}$C. The larger deformation length obtained from the DWBA analysis could be explained by including the excitation of $^7$Be in a coupled-channel analysis. The breakup cross section of $^7$Be is estimated to be less than 10$\%$ of the reaction cross section. The intrinsic deformation length obtained for the $^{12}$C$^*$ (4.439 MeV) state is $\delta _2$ = 1.37 fm. The total reaction cross section deduced from the analysis agrees very well with Wong's calculations for similar weakly bound light nuclei on $^{12}$C target., Comment: 8 pages, 5 figures

The anomaly in lithium abundance is a well-known unresolved problem in nuclear astrophysics. A recent revisit to the problem tried the avenue of resonance enhancement to account for the primordial $^7$Li abundance in standard big-bang nucleosynthesis (BBN). Prior measurements of the $^7$Be(d,p)$^8$Be* reaction could not account for the individual contributions of the different excited states involved, particularly at higher energies close to the Q-value of the reaction. We carried out an experiment at HIE-ISOLDE, CERN to study this reaction at E$_{cm}$ = 7.8 MeV, populating excitations up to 22 MeV in $^8$Be for the first time. The angular distributions of the several excited states have been measured and the contributions of the higher excited states in the total cross section at the relevant big-bang energies were obtained by extrapolation to the Gamow window using the TALYS code. The results show that by including the contribution of the 16.63 MeV state, the maximum value of the total S-factor inside the Gamow window comes out to be 167 MeV b as compared to earlier estimate of 100 MeV b. However, this still does not account for the lithium discrepancy., Comment: 5 pages, 5 figures

The nature of dark matter and properties of neutrinos are among the most pressing issues in contemporary particle physics. The dual-phase xenon time-projection chamber is the leading technology to cover the available parameter space for Weakly Interacting Massive Particles (WIMPs), while featuring extensive sensitivity to many alternative dark matter candidates. These detectors can also study neutrinos through neutrinoless double-beta decay and through a variety of astrophysical sources. A next-generation xenon-based detector will therefore be a true multi-purpose observatory to significantly advance particle physics, nuclear physics, astrophysics, solar physics, and cosmology. This review article presents the science cases for such a detector., Comment: 77 pages, 40 figures, 1262 references

In this article, a detailed investigation has been done for the long lived gamma activity due to neutron emitting experiments. These calculations mainly focused on the experiments used for energy calibration purposes. Calibrated energy is one of the most essential features of any accelerator facility. Several experiments have been used for this purpose. Generally, experiments having sharp curvature change in cross section of yield are used. Neutron emitting experiments are one of such. Around the globe reactions like $^7Li(p,n)$, $^{13}C(p,n)$, $^{19}F(p,n)$, $^{27}Al(p,n)$ etc. are used to calibrate energy of the beam with accelerator terminal voltage. Neutrons coming from these experiments can interact with surrounding elements. These interactions with neutrons can create long lived gamma activity which may interfere with future measurements. The present study has been done keeping in mind the new Facility for Research in Experimental Nuclear Astrophysics (FRENA) at Saha Institute of Nuclear Physics. It is a 3MV tandetron low energy high current machine.

Precise and accurate measurements of the beam energy delivered to the experimental halls at the Thomas Jefferson Accelerator Facility (Jefferson Lab) is required by many experiments for proper data analysis and physics event reconstruction. During the 6 GeV era of Jefferson Lab, the energy delivered to experimental Hall A was determined to 2E-4 dE/E with multiple measurements; but after the machine was upgraded to 12 GeV, the accelerator's beam energy calculations needed to be re-calibrated. In order to link the 6 GeV era calibrations to the 12 GeV era, the Hall A ARC energy measurement system was left unmodified. After the upgrade, this system was used to determine the absolute beam energy being delivered into Hall A and find the new calibrations for the main machine. To ensure the validity of these results, they have been cross checked using elastic scattering data as well as spin precession data., Comment: 6 pages, 8 figures

The origin of the large $\alpha$ particle production and incomplete fusion in reactions involving weakly-bound $\alpha$+$x$ cluster nuclei still remains unresolved. While the (two-step) process of breakup followed by capture of the ``free" complementary fragment ($x$) is widely believed to be responsible, a few recent studies suggest the dominant role of (direct) cluster stripping. To achieve an unambiguous experimental discrimination between these two processes, a coincidence measurement between the outgoing $\alpha$ particles and $\gamma$ rays from the heavy residues has been performed for the $^7$Li($\alpha$+triton)+$^{93}$Nb system. Proper choice of kinematical conditions allowed for the first time a significant population of the region accessible only to the direct triton stripping process and not to breakup followed by the capture of the ``free'' triton (from the three-body continuum). This result, also supported by a cluster-transfer calculation, clearly establishes the dominance of the direct cluster-stripping mechanism in the large alpha production.

The longitudinal asymmetry arises in relativistic heavy ion collisions due to fluctuation in the number of participating nucleons. This asymmetry causes a shift in the center of mass rapidity of the participant zone. The rapidity shift as well as the longitudinal asymmetry have been found to be significant at the top LHC energy for collisions of identical nuclei. We study the longitudinal asymmetry and its effect on charged particle rapidity distribution and anisotropic flow parameters at relatively lower RHIC energies using a model calculation. The rapidity shift is found to be more pronounced for peripheral collisions, smaller systems and also for lower beam energies due to longitudinal asymmetry. A detailed study has been done by associating the average rapidity shift to a polynomial relation where the coefficients of this polynomial characterize the effect of the asymmetry. We show that the rapidity shift may affect observables significantly at RHIC energies., Comment: 6 pages, 8 figures

The three-dimensional structure of nucleons (protons and neutrons) is embedded in so-called generalized parton distributions, which are accessible from deeply virtual Compton scattering. In this process, a high energy electron is scattered off a nucleon by exchanging a virtual photon. Then, a highly-energetic real photon is emitted from one of the quarks inside the nucleon, which carries information on the quark's transverse position and longitudinal momentum. By measuring the cross-section of deeply virtual Compton scattering, Compton form factors related to the generalized parton distributions can be extracted. Here, we report the observation of unpolarized deeply virtual Compton scattering off a deuterium target. From the measured photon-electroproduction cross-sections, we have extracted the cross-section of a quasi-free neutron and a coherent deuteron. Due to the approximate isospin symmetry of quantum chromodynamics, we can determine the contributions from the different quark flavours to the helicity-conserved Compton form factors by combining our measurements with previous ones probing the proton's internal structure. These results advance our understanding of the description of the nucleon structure, which is important to solve the proton spin puzzle.

Resistive heating and mechanical rolling methods have been employed to prepare isotopically enriched thin target foils of 116Sn (~380 \mu g/cm2), 124Sn(~400 \mu g/cm2) and thicker foils of 112Sn (1.7 mg/cm2),120Sn (1.6 mg/cm2),respectively. Preparation of enriched targets with small amount of material, selection of releasing agent for thin targets and separation of deposited material insolvent were among the several challenges while fabrication of the thin targets. Uniformity of the targets has been measured using 241Am {\alpha}-source. NaCl has been used as releasing agent in preparation of the thin targets. These targets have been successfully used in nuclear physics experiments at VECC.

Understanding the nucleon spin structure in the regime where the strong interaction becomes truly strong poses a challenge to both experiment and theory. At energy scales below the nucleon mass of about 1 GeV, the intense interaction among the quarks and gluons inside the nucleon makes them highly correlated. Their coherent behaviour causes the emergence of effective degrees of freedom, requiring the application of non-perturbative techniques, such as chiral effective field theory. Here, we present measurements of the neutron's generalized spin-polarizabilities that quantify the neutron's spin precession under electromagnetic fields at very low energy-momentum transfer squared down to 0.035 GeV$^2$. In this regime, chiral effective field theory calculations are expected to be applicable. Our data, however, show a strong discrepancy with these predictions, presenting a challenge to the current description of the neutron's spin properties., Comment: V1: initial version submitted to Nature Physics. V2: Published version. 16 pages, 7 figures. Additional material: 4 data tables (18 pages) V3: Typo corrected in author list. Paper content unchanged

Detailed characterization of the newly available plastic scintillator (EJ-299-33A) having the pulse shape discrimination (PSD) property has been carried out in case of a large-sized detector (5 in.$\times$5 in.). The pulse height response of the scintillator for nearly mono-energetic neutrons has been reported in case of neutron energies E$_n$ =3, 6 and 9 MeV. Important properties (figure-of-merit (FOM), time resolution, detection efficiency) of the detector has been compared with a commonly used liquid organic scintillator based detector of the same size coupled to the same PMT for uniformity in comparison. The results show that the plastic scintillator detector has about 12$\%$ better time resolution. However, the FOM and detection efficiency were found to be lower than that of the liquid scintillator detector by 40 - 50$\%$ and $\sim $25$\%$, respectively. The possibility of using the new plastic scintillator in large-scale nuclear physics experiments has been pointed out.

Time-stamped data have been used to estimate the decay half-lives of radioactive 118mSb and 64,66,68Ga nuclei. These nuclei are populated through the reaction 4He (Elab = 32 MeV) + nat In and p (Elab = 10 MeV) + natZn, respectively. The g -rays emitted by the excited daughter nuclei are detected by a single high purity germanium (HPGe) detector and the data are acquired using a CAEN 5780M desktop digitizer. Half-lives of different orders of magnitudes for the above mentioned nuclei are obtained from both the decay of parent and the growth of daughter nuclei. It is observed that the half-lives obtained from both these techniques match fairly well and also are consistent with the reported values. It is demonstrated that the time-stamped data can be useful while studying certain half-lives which are too long for measurement using in-beam electronic technique and too short for decay studies in off-beam methods. The data also have a special relevance for constant monitoring of beam current and beam-tuning., Comment: 13 Pages, 4 figures

A large 4$\pi$ array of charged particle detectors has been developed at Variable Energy Cyclotron Centre to facilitate high resolution charged particle reaction and spectroscopy studies by detecting event-by-event the charged reaction products emitted in heavy ion reactions at energy $\sim$ 10-60 MeV/A. The forward part ($\theta \sim \pm $ $7^{0}$ - $\pm 45^{0}$) of the array consists of 24 highly granular, high resolution charged particle telescopes, each of which is made by three layers [single sided silicon strip($\Delta$E) + double sided silicon strip (E/$\Delta$E) + CsI(Tl)(E)]of detectors. The backward part of the array consists of 112 CsI(Tl) detectors which are capable of detecting primarily the light charged particles (Z $\le$ 2) emitted in the angular range of $\theta \sim \pm $ $45^{0}$ - $\pm 175^{0}$. The extreme forward part of the array ($\theta \sim \pm $ $3^{0}$ - $\pm 7^{0}$) is made up of 32 slow-fast plastic phoswich detectors that are capable of detecting light (Z $\le$2) and heavy charged particles (3 $\le$ Z $\lesssim$ 20) as well as handling high count rates. The design, construction and characterization of the array has been described., Comment: Paper has been submitted in NIMA

The slowest reaction in the CNO cycle 14N(p, gamma)15O has been studied by populating the E^lab_p =278 keV (E^r_c.m.=259 keV) proton capture resonant state of ^{15}O at 7556 keV. The strength of the resonance has been determined from the experimental data. The level lifetime of the sub-threshold resonant state at Ex=6792 keV, as well as the lifetimes of the 5181 keV and 6172 keV states, have been measured using the Doppler shift attenuation method (DSAM). The structural properties of the nucleus ^{15}O, such as, the level energies, transition strengths, level lifetimes, and spectroscopic factors, have been calculated theoretically by using the large basis shell model, which agrees reasonably well with the present as well as the previous experimental data., Comment: 10 pages, 9 figures, Accepted for publication in Physical Review C

The Lanthanum Halide scintillator detectors have been widely used for nuclear spectroscopy experiments because of their excellent energy and time resolutions. Despite having these advantages, the intrinsic alpha and beta contaminations in these scintillators pose a severe limitation in their usage in rare-event detections. In the present work, pulse shape discrimination (PSD) with a fast digitizer has been shown to be an efficient method to separate the effect of alpha contamination from the spectrum. The shape of the beta spectrum has been generated with the help of Monte Carlo based simulation code, and its contribution has been eliminated from the spectrum. The reduction in the background events generated by both intrinsic beta and alpha activities has been demonstrated. The present study will encourage the application of these detectors in low cross-section measurement experiments relevant to nuclear astrophysics., Comment: 15 pages, 6 figures

High-spin states of neutron deficient Trans-Lead nucleus $^{204}$At were populated up to $\sim 8\,{\rm MeV}$ excitation through the $^{12}$C + $^{197}$Au fusion evaporation reaction. Decay of the associated levels through prompt and delayed $\gamma$-ray emissions were studied to evaluate the underlying nuclear structure. The level scheme, which was partly known, was extended further. An isomeric $16^+$ level with observed lifetime $\tau=52 \pm 5\, {\rm ns}$, was established from our measurements. Attempts were made to interpret the excited states based on multi quasiparticle and hole structures involving $2f_{5/2}$, $1h_{9/2}$, and $1i_{13/2}$ shell model states, along with moderate core excitation. Magnetic dipole band structure over the spin parity range:~$16^+ - 23^+$ was confirmed and evaluated in more detail, including the missing cross-over $E2$ transitions. Band-crossing along the shears band was observed and compared with the evidence of similar phenomena in the neighbouring neutron deficient $^{202}$Bi, $^{205}$Rn isotones and the $^{203}$At isotope. Based on comparison of the measured $B(M1)/B(E2)$ values for transitions along the band with the semiclassical model based estimates, the shears band of $^{204}$At was established along with the level scheme., Comment: This preprint has not undergone peer review or any post-submission improvements or corrections. The Version of Record of this article is published in The European Physical Journal A and is available online at https://doi.org/10.1140/epja/s10050-022-00809-4

The gamma-ray background in the indoor environment has been measured up to 3 MeV to evaluate the feasibility of studying low cross-section (nanobarn to picobarn range) astrophysical reactions at the Facility for Research in Experimental Nuclear Astrophysics (FRENA), Saha Institute of Nuclear Physics, Kolkata. An n-type coaxial HPGe detector with 20% relative efficiency has been placed at different locations in the accelerator and beam halls for the measurement. The measured activity has been compared with that at two laboratories (with standard brick walls) with and without passive and active radiation shielding. As the halls at FRENA are well shielded by concrete, the contribution of the shielding in indoor gamma-ray background has been delineated by simulation using a 4p-geometry model., Comment: 20 pages with 14 figures; Accepted for publication in JINST

Short Range Correlations (SRCs) have been identified as being responsible for the high momentum tail of the nucleon momentum distribution, n(k). Hard, short-range interactions of nucleon pairs generate the high momentum tail and imprint a universal character on n(k) for all nuclei at large momentum. Triple coincidence experiments have shown a strong dominance of np pairs, but these measurements involve large final state interactions. This paper presents the results from Jefferson Lab experiment E08014 which measured inclusive electron scattering cross-section from Ca isotopes. By comparing the inclusive cross section from 48Ca to 40Ca in a kinematic region dominated by SRCs we provide a new way to study the isospin structure of SRCs., Comment: 7 pages, 3 figures

The 12C(20Ne,16O)16O {\alpha}-transfer reaction at Elab=150 MeV is first time used to determine the ANC of the 6.92 MeV and 7.12 MeV states of 16O. The 20Ne+ 12C potential parameters are also obtained from elastic scattering. The direct reaction code FRESCO is used to determine the {\alpha}-spectroscopy factor (S{\alpha} ) of the three states of 16O (6.92 MeV, 7.12 MeV and 11.52 MeV) and ANC of the two states (6.92 MeV and 7.12 MeV) of 16O. The extracted ANC and S{\alpha} are compareable to previous measurements., Comment: 8 pages and 18 figures

Two opposite parity dipole bandlike structures DB I and DB II of $^{142}$Eu are investigated by the Indian National Gamma Array (INGA), using the fusion evaporation reaction $^{31}$P + $^{116}$Cd @ 148 MeV. The decreasing trend as well as magnitude of the measured $B(M1)$ and $B(E2)$ transition rates of the band DB II has been reproduced well within the shears mechanism with the principal axis cranking model calculations. This calculation reflects the fact that the maximum contribution of the angular momentum of the states in DB II has been generated from the magnetic rotation (MR) phenomenon. The enhanced $B(E1)$ rates of the connecting $E1$ transitions from the states of DB II to DB I are demanding the octupole correlation due to the involvement of the octupole driving pair of orbitals $\pi{h_{11/2}}$ and $\pi{d_{5/2}}$ as evident from the quasiparticle alignment ($i_{x}$), the experimental routhians (e$^{'}$) and the calculated neutron and proton quasiparticle energies against the rotational frequency ($\omega$)., Comment: 6 pages, 5 figures

An electrically cooled Broad Energy Germanium (BEGe) detector has been characterized in the energy range E$_{\gamma}$ $\sim$ 0.122 - 7 MeV by utilizing the $\gamma$- rays emitted by a short-lived resonance state in $^{15}$O populated through $^{14}$N(p,$\gamma$) reaction and standard radioactive source ($^{152}$Eu). The experimental results have been reproduced through simulations with GEANT4 code, including vendor specified detector geometry along with the detailed construction of the target holder flange, to delineate the effects of the holder at various energies and detector position. Later the efficiency with a bare point source has been simulated. It has been found that the electrically cooled BEGe detector is suitable for usage in the $\gamma$-ray spectroscopy as well as for the study of resonance phenomena in nuclear astrophysics., Comment: 18 pages including 10 figures

A silicon-tungsten (Si-W) sampling calorimeter, consisting of 19 alternate layers of silicon pad detectors (individual pad area of 1~cm$^2$) and tungsten absorbers (each of one radiation length), has been constructed for measurement of electromagnetic showers over a large energy range. The signal from each of the silicon pads is readout using an ASIC with a dynamic range from $-300$~fC to $+500$~fC. Another ASIC with a larger dynamic range, $\pm 600$~fC has been used as a test study. The calorimeter was exposed to pion and electron beams at the CERN Super Proton Synchrotron (SPS) to characterise the response to minimum ionising particles (MIP) and showers from electromagnetic (EM) interactions. Pion beams of 120 GeV provided baseline measurements towards the understanding of the MIP behaviour in the silicon pad layers, while electron beams of energy from 5 GeV to 60 GeV rendered detailed shower profiles within the calorimeter. The energy deposition in each layer, the longitudinal shower profile, and the total energy deposition have been measured for each incident electron energy. Linear behaviour of the total measured energy ($E$) with that of the incident particle energy ($E_{0}$) ensured satisfactory calorimetric performance. For a subset of the data sample, selected based on the cluster position of the electromagnetic shower of the incident electron, the dependence of the measured energy resolution on $E_{0}$ has been found to be $\sigma/E = (15.36/\sqrt{E_0(\mathrm{GeV)}} \oplus 2.0) \%$., Comment: 14 pages, 13 figures, test beam performances of focal prototype with pad sensors only

The spin-structure functions $g_1$ and $g_2$, and the spin-dependent partial cross-section $\sigma_\mathrm{TT}$ have been extracted from the polarized cross-sections differences, $\Delta \sigma_{\parallel}\hspace{-0.06cm}\left(\nu,Q^{2}\right)$ and $\Delta \sigma_{\perp}\hspace{-0.06cm}\left(\nu,Q^{2}\right)$ measured for the $\vec{^\textrm{3}\textrm{He}}(\vec{\textrm{e}},\textrm{e}')\textrm{X}$ reaction, in the E97-110 experiment at Jefferson Lab. Polarized electrons with energies from 1.147 to 4.404 GeV were scattered at angles of 6$^{\circ}$ and 9$^{\circ}$ from a longitudinally or transversely polarized $^{3}$He target. The data cover the kinematic regions of the quasi-elastic, resonance production and beyond. From the extracted spin-structure functions, the first moments $\overline{\Gamma_1}\hspace{-0.06cm}\left(Q^{2}\right)$, $\Gamma_2\hspace{-0.06cm}\left(Q^{2}\right)$ and $I_{\mathrm{TT}}\hspace{-0.06cm}\left(Q^{2}\right)$ are evaluated with high precision for the neutron in the $Q^2$ range from 0.035 to 0.24~GeV$^{2}$. The comparison of the data and the chiral effective field theory predictions reveals the importance of proper treatment of the $\Delta$ degree of freedom for spin observables., Comment: 7 pages, 5 figures, 3 tables. Version published in Phys. Lett. B

Due to the lack of free neutron targets, studies of the structure of the neutron are typically made by scattering electrons from either $^2$H or $^3$He targets. In order to extract useful neutron information from a $^3$He target, one must understand how the neutron in a $^3$He system differs from a free neutron by taking into account nuclear effects such as final state interactions and meson exchange currents. The target single spin asymmetry $A_y^0$ is an ideal probe of such effects, as any deviation from zero indicates effects beyond plane wave impulse approximation. New measurements of the target single spin asymmetry $A_y^0$ at $Q^2$ of 0.46 and 0.96 (GeV/$c)^2$ were made at Jefferson Lab using the quasi-elastic $^3\mathrm{He}^{\uparrow}(e,e'n)$ reaction. Our measured asymmetry decreases rapidly, from $>20\%$ at $Q^2=0.46$ (GeV/$c)^2$ to nearly zero at $Q^2=0.96$ (GeV$/c)^2$, demonstrating the fall-off of the reaction mechanism effects as $Q^2$ increases. We also observed a small $\epsilon$-dependent increase in $A_y^0$ compared to previous measurements, particularly at moderate $Q^2$. This indicates that upcoming high $Q^2$ measurements from the Jefferson Lab 12 GeV program can cleanly probe neutron structure from polarized $^3$He using plane wave impulse approximation., Comment: 6 pages, 5 figures

Experimental cross sections for the $^4He(e,e'p)X$ reaction up to a missing momentum of 0.632 GeV/$c$ at $x_B=1.24$ and $Q^2$=2(GeV/$c$)$^2$ are reported. The data are compared to Relativistic Distorted Wave Impulse Approximation(RDWIA) calculations for $^4He(e,e'p)^3H$ channel. Significantly more events in the triton mass region are measured for $p_{m}$$>$0.45 GeV/$c$ than are predicted by the theoretical model, suggesting that the effects of initial-state multi-nucleon correlations are stronger than expected by the RDWIA model., Comment: Submitted to PRC

The present work reported a conclusive evidence for anti-magnetic rotational (AMR) band in an odd-odd nucleus 142Eu. Parity of the states of a quadrupole sequence in 142Eu was firmly identified from polarization measurements using the Indian National Gamma Array and lifetimes of some of the states in the same structure were measured using the Doppler shift attenuation method. The decreasing trends of the deduced quadrupole transition strength B(E2) with spin, along with increasing J(2) / B(E2) values conclusively established the origin of these states as arising from Antimagnetic rotation. The results were well reproduced by numerical calculations within the framework of a semi-classical geometric model.

The decay of odd-odd $^{150}$Pm has been studied by populating the nucleus with the $^{150}$Nd(p,n)$^{150}$Pm reaction at E$_{beam}$ = 8.0 MeV using 97$\%$ enriched $^{150}$Nd target. The presence of an isomeric state with $\beta$ decay half life of 2.2(1) h could be identified in $^{150}$Pm by following the half lives of the observed $\gamma$ transitions. The decay of the isomer to the excited levels of $^{150}$Sm has been confirmed by observing the $\gamma - \gamma$ coincidence with the VENUS array of six Compton suppressed Clover HPGe detectors. The $\beta$ decay end-point energies corresponding to the decay from the $^{150g}$Pm and $^{150m}$Pm have been measured using a $\beta-\gamma$ coincidence setup of two thin window Planar HPGe detectors and four Clover HPGe detectors of the VENUS array. The systematics of the similar isomeric states in neighboring nuclei has been studied to understand the underlying structure of these states. Shell model calculation has been performed by using OXBASH code which indicates the presence of a 5$^-$ isomeric state at very low excitation in the nucleus. The calculation also suggests hindered electromagnetic decay of this isomer and supports the possibility of its $\beta$ decay to the excited levels of $^{150}$Sm., Comment: 15 pages, 13 figures

The experiment E94-107 in Hall A at Jefferson Lab started a systematic study of high resolution hypernuclear spectroscopy in the 0p-shell region of nuclei such as the hypernuclei produced in electroproduction on 9Be, 12C and 16O targets. In order to increase counting rates and provide unambiguous kaon identification two superconducting septum magnets and a ring-imaging Cherenkov detector were added to the Hall A standard equipment. The high-quality beam, the good spectrometers and the new experimental devices allowed us to obtain very good results. For the first time, measurable strength with sub-MeV energy resolution was observed for the core-excited states of Lambda 12B. A high-quality Lambda 16N hypernuclear spectrum was likewise obtained. A first measurement of the Lambda binding energy for Lambda 16N, calibrated against the elementary reaction on hydrogen, was obtained with high precision, 13.76 +/- 0.16 MeV. Similarly, the first Lambda 9Li hypernuclear spectrum shows general agreement with theory (distorted-wave impulse approximation with the SLA and BS3 electroproduction models and shell-model wave functions). Some disagreement exists with respect to the relative strength of the states making up the first multiplet. A Lambda separation energy of 8.36 MeV was obtained, in agreement with previous results. It has been shown that the electroproduction of hypernuclei can provide information complementary to that obtained with hadronic probes and the gamma-ray spectroscopy technique., Comment: 27 pages, 18 figures, submitted to Physical Review C

We report on a precise measurement of double-polarization asymmetries in electron-induced breakup of $^3\mathrm{He}$ proceeding to $\mathrm{pd}$ and $\mathrm{ppn}$ final states, performed in quasi-elastic kinematics at $Q^2 = 0.25\,(\mathrm{GeV}/c)^2$ for missing momenta up to $250\,\mathrm{MeV}/c$. These observables represent highly sensitive tools to investigate the electromagnetic and spin structure of $^3\mathrm{He}$ and the relative importance of two- and three-body effects involved in the breakup reaction dynamics. The measured asymmetries cannot be satisfactorily reproduced by state-of-the-art calculations of $^3\mathrm{He}$ unless their three-body segment is adjusted, indicating that the spin-dependent part of the nuclear interaction governing the three-body breakup process is much smaller than previously thought., Comment: 5 pages, 3 figures, submitted to Phys. Rev. Lett

We present new data probing short-range correlations (SRCs) in nuclei through the measurement of electron scattering off high-momentum nucleons in nuclei. The inclusive 4He/3He cross section ratio is observed to be both x and Q2 independent for 1.5 < x < 2, confirming the dominance of two- nucleon (2N) short-range correlations (SRCs). For x > 2, our data do not support a previous claim of three-nucleon (3N) correlation dominance. While contributions beyond those from stationary 2N- SRCs are observed, our data show that isolating 3N-SRCs is more complicated than for 2N-SRCs., Comment: 6 pages, 2 figures, new experimental results from JLab E08-014

$[Background]$ Measurements of the neutron charge form factor, $G^n_E$, are challenging due to the fact that the neutron has no net charge. In addition, measurements of the neutron form factors must use nuclear targets which require accurately accounting for nuclear effects. Extracting $G^n_E$ with different targets and techniques provides an important test of our handling of these effects. $[Purpose]$ The goal of the measurement was to use an inclusive asymmetry measurement technique to extract the neutron charge form factor at a four-momentum transfer of $1~(\rm{GeV/c})^2$. This technique has very different systematic uncertainties than traditional exclusive measurements and thus serves as an independent check of whether nuclear effects have been taken into account correctly. $[Method]$ The inclusive quasi-elastic reaction $^3\overrightarrow{\rm{He}}(\overrightarrow{e},e')$ was measured at Jefferson Lab. The neutron electric form factor, $G_E^n$, was extracted at $Q^2 = 0.98~(\rm{GeV/c})^2$ from ratios of electron-polarization asymmetries measured for two orthogonal target spin orientations. This $Q^2$ is high enough that the sensitivity to $G_E^n$ is not overwhelmed by the neutron magnetic contribution, and yet low enough that explicit neutron detection is not required to suppress pion production. $[Results]$ The neutron electric form factor, $G_E^n$, was determined to be $0.0414\pm0.0077\;{(stat)}\pm0.0022\;{(syst)}$; providing the first high precision inclusive extraction of the neutron's charge form factor. $[Conclusions]$ The use of the inclusive quasi-elastic $^3\overrightarrow{\rm{He}}(\overrightarrow{e},e')$ with a four-momentum transfer near $1~(\rm{GeV/c})^2$ has been used to provide a unique measurement of $G^n_E$. This new result provides a systematically independent validation of the exclusive extraction technique results., Comment: 7 pages, 2 figures, 2 tables

The proton is composed of quarks and gluons, bound by the most elusive mechanism of strong interaction called confinement. In this work, the dynamics of quarks and gluons are investigated using deeply virtual Compton scattering (DVCS): produced by a multi-GeV electron, a highly virtual photon scatters off the proton which subsequently radiates a high energy photon. Similarly to holography, measuring not only the magnitude but also the phase of the DVCS amplitude allows to perform 3D images of the internal structure of the proton. The phase is made accessible through the quantum-mechanical interference of DVCS with the Bethe-Heitler (BH) process, in which the final photon is emitted by the electron rather than the proton. We report herein the first full determination of the BH-DVCS interference by exploiting the distinct energy dependences of the DVCS and BH amplitudes. In the high energy regime where the scattering process is expected to occur off a single quark in the proton, these accurate measurements show an intriguing sensitivity to gluons, the carriers of the strong interaction.

We searched for the bound state of the neutron-rich $\Lambda$-hypernucleus ${}^{6}_{\Lambda}$H, using the ${}^{6}$Li($\pi^{-}, K^{+}$)X double charge-exchange reaction at a $\pi^{-}$ beam momentum of 1.2 GeV/c at J-PARC. A total of $1.4 \times 10^{12}$ $\pi^{-}$ was driven onto a ${}^{6}$Li target of 3.5-g/$\rm cm^2$ thickness. No event was observed below the bound threshold, i.e., the mass of ${}^{4}_{\Lambda}$H + 2n, in the missing-mass spectrum of the ${}^{6}$Li($\pi^{-}, K^{+}$)X reaction in the $2^{\circ}$ < $\theta_{\pi K}$ < $20^{\circ}$ angular range. Furthermore, no event was found up to 2.8 MeV/$c^2$ above the bound threshold. We obtained the the double-differential cross section spectra of the ${}^{6}$Li($\pi^{-}, K^{+}$)X reaction in the angular range of $2^{\circ}$ < $\theta_{\pi K}$ < $14^{\circ}$. An upper limit of 0.56 nb/sr (90% C.L.) was obtained for the production cross section of the ${}^{6}_{\Lambda}$H hypernucleus bound state. In addition, not only the bound state region, but also the $\Lambda$ continuum region and part of the $\Sigma^{-}$ quasi-free production region of the ${}^{6}$Li($\pi^{-}, K^{+}$)X reaction, were obtained with high statistics. The present missing-mass spectrum will facilitate the investigation of the $\Sigma^{-}$-nucleus optical potential for $\Sigma^{-}$-${}^{5}$He through spectrum shape analysis., Comment: 24 pages, 17 figures

We report the first longitudinal/transverse separation of the deeply virtual exclusive $\pi^0$ electroproduction cross section off the neutron and coherent deuteron. The corresponding four structure functions $d\sigma_L/dt$, $d\sigma_T/dt$, $d\sigma_{LT}/dt$ and $d\sigma_{TT}/dt$ are extracted as a function of the momentum transfer to the recoil system at $Q^2$=1.75 GeV$^2$ and $x_B$=0.36. The $ed \to ed\pi^0$ cross sections are found compatible with the small values expected from theoretical models. The $en \to en\pi^0$ cross sections show a dominance from the response to transversely polarized photons, and are in good agreement with calculations based on the transversity GPDs of the nucleon. By combining these results with previous measurements of $\pi^0$ electroproduction off the proton, we present a flavor decomposition of the $u$ and $d$ quark contributions to the cross section., Comment: 6 pages, 6 figures, Submitted to Phys. Rev. Lett

Lifetimes of the states in the quadrupole structure in 143Eu have been measured using the Doppler shift attenuation method as well as parity of the states in the sequence has been firmly identified from polarization measurement using the Indian National Gamma Array. The decreasing trends of the deduced quadrupole transition strength B(E2) with spin, along with increasing J (2) /B(E2) values before band crossing, conclusively establish the origin of these states as arising out of antimagnetic rotation. The abrupt increase in the B(E2) values after the band crossing in the quadrupole band, a novel feature observed in the present experiment, may indicates the crossing of different shears configurations resulting in re-opening of shears structure. The results are well reproduced by numerical calculation within the framework of semi-classical geometric model., Comment: 6 pages, 4 postscript figures