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Nuclear Theory·nucl-th

Monday·March 15, 2021

6 papers—4 primary·2 cross-listed

All6Primary4Cross-lists2
  1. 01

    On the timescale of quasi fission and Coulomb fission

    T. Nandi · H. C. Manjunatha · P. S. Damodara Gupta · N. Sowmya · N. Manjunatha · K. N. Sridhara · L. Seenappa

    Coulomb fission mechanism may take place if the maximum Coulomb-excitation energy transfer in a reaction exceeds the fission barrier of either the projectile or target. This condition is satisfied by all the reactions used for the earlier blocking measurements except one reaction 208 Pb + Natural Ge crystal, where the measured timescale was below the measuring limit of the blocking measurements < 1 as. Hence, inclusion of the Coulomb fission in the data analysis of the blocking experiments leads us to interpret that the measured time longer than a few attoseconds (about 2-2.5 as) is nothing but belonging to the Coulomb fission timescale and shorter than 1 as are due to the quasifission. Consequently, this finding resolves the critical discrepancies between the fission timescale measurements using the nuclear and blocking techniques. This, in turn, validates the fact that the quasifission timescale is indeed of the order of zeptoseconds in accordance with the nuclear experiments and theories. It thus provides a radical input in understanding the reaction mechanism for heavy element formation via fusion evaporation processes

    nucl-thPramana(2022)·4 citations
  2. 02

    Systematics of semi-microscopic proton-nucleus optical potential at low energies relevant to nuclear astrophysics

    E. Vagena🇬🇷 · M. Axiotis🇬🇷 · P. Dimitriou🇬🇷

    Astrophysical models studying the origin of the p-nuclei require knowledge of the reaction rates of photodisintegrations and capture reactions. Since experimental data at astrophysically relevant energies are limited, reaction rate calculations rely on Hauser-Feshbach (HF) theory predictions. The HF theory requires nuclear physics input such as masses, level densities, -ray strength functions and proton-nucleus optical potentials (pOMP). The scope of this work is to improve a global semi-microscopic pOMP at energies relevant to the p-process. This is achieved by adjusting the normalization parameters of the OMP to all available proton-capture cross sections measured at low energies. By establishing the systematic behaviour of these parameters, one expects to enhance the predictive power of the pOMP when expanding to mass regions where no data exists. The HF calculations were obtained using TALYS code. The normalization parameters for the real and imaginary central potentials ( and ) were adjusted to fit the proton data in the energy range where the cross-section are independent of the other nuclear inputs. Results show that the parameter has a strong mass dependence that can be described by a second-degree polynomial function for A 100 and an exponential increase for 100 < A < 162. Though variations of the have a smaller effect on the calculations, a global increase by 50 improves the results for certain nuclei without affecting the rest of the cases. The resulting adjustment functions were obtained by fitting all suitable proton data and can be used with reasonable confidence to generate the global semi-microscopic pOMP for nuclei in the medium to heavy mass region. For better statistics, more low-energy (p,) cross section data are needed for heavier nuclei with mass A 100.

    nucl-thPRC(2021)·7 citations
  3. 03

    Supremacy of optimal beam energy for synthesis of superheavy elements

    H.C. Manjunatha · N. Sowmya · P.S.Damodara Gupta · L. Seenappa · T. Nandi

    Besides right choice of entrance channel, selection of optimal beam energies for synthesis of superheavy elements plays a crucial role. A thorough investigation with the advanced statistical and dinuclear system models on all the experiments performed for the synthesis of the successful superheavy elements Z=104-118 and failed superheavy elements Z=119-120 leads us to infer that improper choice of the beam energies may be responsible for too low production cross sections to measure and thus the cause for the debacle. We have predicted the optimal beam energies to obtain the maximum production cross sections for all the reactions used for the superheavy elements Z=104-120. Hope exploitation of these predictions may be on the cards soon to extend the periodic table for the eighth period

    nucl-th1 citation
  4. 04

    Speed of sound and baryon cumulants in heavy-ion collisions

    Agnieszka Sorensen🇺🇸 · Dmytro Oliinychenko🇺🇸 · Volker Koch🇺🇸 · Larry McLerran🇺🇸

    We present a method that may allow an estimate of the value of the speed of sound as well as its logarithmic derivative with respect to the baryon number density in matter created in heavy-ion collisions. To this end, we utilize well-known observables: cumulants of the baryon number distribution. In analyses aimed at uncovering the phase diagram of strongly interacting matter, cumulants gather considerable attention as their qualitative behaviour along the explored range of collision energies is expected to aid in detecting the QCD critical point. We show that the cumulants may also reveal the behavior of the speed of sound in the temperature and baryon chemical potential plane. We demonstrate the applicability of such estimates within two models of nuclear matter, and explore what might be understood from known experimental data.

    nucl-thPRL(2021)·49 citations
  5. 05

    Signatures of Moat Regimes in Heavy-Ion Collisions

    Robert D. Pisarski🇺🇸 · Fabian Rennecke🇺🇸

    Heavy-ion collisions at small beam energies have the potential to reveal the rich phase structure of QCD at nonzero temperature and density. Among the possible phases are regimes which feature periodic modulations of the spatial structure, where the energy spectrum is shaped like a moat, with the minimum of the energy over a sphere at nonzero momentum. We argue that if the matter created in heavy-ion collisions traverses such a regime, it can produce a characteristic momentum dependence of particle number and their correlations. As an explicit example, we consider a quantum pion liquid phase to compute these quantities on the freeze-out surface. These results can serve as a first guideline for a systematic search of spatially modulated phases in heavy-ion collisions.

    ↳ hep-phnucl-thPRL(2021)·69 citations
  6. 06

    Cold quark matter at N3LO: soft contributions

    Tyler Gorda🇩🇪 · Aleksi Kurkela🇳🇴 · Risto Paatelainen🇫🇮 · Saga Säppi🇮🇹 · Aleksi Vuorinen🇫🇮

    High-order perturbative calculations for thermodynamic quantities in QCD are complicated by the physics of dynamical screening that affects the soft, long-wavelength modes of the system. Here, we provide details for the evaluation of this soft contribution to the next-to-next-to-next-to-leading order (N3LO) pressure of high-density, zero-temperature quark matter (QM), complementing our accompanying paper in arXiv:2103.05658. Our calculation requires the determination of the pressure of the hard-thermal-loop (HTL) effective theory to full two-loop order at zero temperature, which we go through in considerable detail. In addition to this, we comprehensively discuss the structure of the weak-coupling expansion of the QM pressure, and lay out a roadmap towards the evaluation of the contributions missing from a full N3LO result for this quantity.

    ↳ hep-phnucl-thPRD(2021)·103 citations

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first authorsco-authorsvia INSPIRE