Mon·Jul 24, 2017Monday·July 24, 2017

1. 01*

   A Bayesian analysis of light-front models and the nucleon's charmed sigma term

   T. J. Hobbs🇺🇸 · Mary Alberg🇺🇸 · Gerald A. Miller🇺🇸

   We present the results of a recent analysis to study the nucleon's charm sigma term, ${\sigma }_{c\overline{c}}$. We construct a minimal model in terms of light-front variables and constrain the range of possibilities using extant knowledge from deeply inelastic scattering (DIS) and Bayesian parameter estimation, ultimately computing ${\sigma }_{c\overline{c}}$ in an explicitly covariant manner. We find a close correlation between a possible nonperturbative component of the charm structure function, $F_{2,\mathrm{IC}}^{c\overline{c}}$, and ${\sigma }_{c\overline{c}}$. Independent of prescription for the covariant relativistic quark-nucleon vertex, we determine ${\sigma }_{c\overline{c}}$ under several different scenarios for the magnitude of intrinsic charm (IC) in DIS, namely $⟨x{⟩}_{c+\overline{c}}=0.1\%$, $0.35\%$, and $1\%$, obtaining for these ${\sigma }_{c\overline{c}}=4\pm 4$, $12\pm 13$, and $32\pm 34$ MeV, respectively. These results imply the existence of a reciprocity between the IC parton distribution function (PDF) and ${\sigma }_{c\overline{c}}$ such that new information from either DIS or improved determinations of ${\sigma }_{c\overline{c}}$ could significantly impact constraints to the charm sector of the proton wave function.

   hep-phnucl-thPRD(2017)·12 citations
2. 02*

   Proton decay testing low energy SUSY

   Stefan Pokorski🇵🇱 · Krzysztof Rolbiecki🇵🇱 · Kazuki Sakurai🇵🇱

   We show that gauge coupling unification in SUSY models can make a non-trivial interconnection between collider and proton decay experiments. Under the assumption of precise gauge coupling unification in the MSSM, the low energy SUSY spectrum and the unification scale are intertwined, and the lower bound on the proton lifetime can be translated into upper bounds on SUSY masses. We found that the current limit on $\tau (p\to {\pi }^0{e}^{+})$ already excludes gluinos and winos heavier than $\sim 120$ and 40 TeV, respectively, if their mass ratio is $M_3/M_2\sim 3$. Next generation nucleon decay experiments are expected to bring these upper bounds down to $\sim 10$ and 3 TeV.

   hep-phhep-exPRD(2018)·8 citations
3. 03*

   Top-Tagging at the Energy Frontier

   Zhenyu Han🇺🇸 · Minho Son🇰🇷 · Brock Tweedie🇺🇸

   At proposed future hadron colliders and in the coming years at the LHC, top quarks will be produced at genuinely multi-TeV energies. Top-tagging at such high energies forces us to confront several new issues in terms of detector capabilities and jet physics. Here, we explore these issues in the context of some simple JHU/CMS-type declustering algorithms and the N-subjettiness jet-shape variable tau_32. We first highlight the complementarity between the two tagging approaches at particle-level with respect to discriminating top-jets against gluons and quarks, using multivariate optimization scans. We then introduce a basic fast detector simulation, including electromagnetic calorimeter showering patterns determined from GEANT. We consider a number of tricks for processing the fast detector output back to an approximate particle-level picture. Re-optimizing the tagger parameters, we demonstrate that the inevitable losses in discrimination power at very high energies can typically be ameliorated. For example, percent-scale mistag rates might be maintained even in extreme cases where an entire top decay would sit inside of one hadronic calorimeter cell and tracking information is completely absent. We then study three novel physics effects that will come up in the multi-TeV energy regime: gluon radiation off of boosted top quarks, mistags originating from g -> tt, and mistags originating from q -> (W/Z)q collinear electroweak splittings with subsequent hadronic decays. The first effect, while nominally a nuisance, can actually be harnessed to slightly improve discrimination against gluons. The second effect can lead to effective O(1) enhancements of gluon mistag rates for tight working points. And the third effect, while conceptually interesting, we show to be of highly subleading importance at all energies.

   hep-phhep-exPRD(2018)·3 citations
4. 04*

   $K^{\ast }(892)$ and $\varphi (1020)$ production and their decay into the hadronic medium at the Large Hadron Collider

   V. M. Shapoval🇺🇦 · P. Braun-Munzinger🇩🇪 · Yu. M. Sinyukov🇺🇦

   The production of the $K^{\ast }(892)$ strange resonance in Pb+Pb collisions at $\sqrt{s_{NN}}=2.76$ TeV LHC energy is analyzed within the integrated hydrokinetic model (iHKM) at different equations of state of superdense matter. The similar analysis is done also for the RHIC top energy $\sqrt{s_{NN}}=200$ GeV for comparison purposes. A modification of experimental $K^{\ast }(892)$-identification is studied for different centralities in view of possible re-scattering of the decay products at the afterburner stage of the fireball evolution. We see quite intensive rescattering of the decay products as well as recombination processes for $K^{\ast }(892)$. In addition, the production of the much longer-long-lived $\varphi (1020)$ resonance with hidden strange quark content is investigated.

   hep-phhep-exnucl-exnucl-thNPA(2017)·20 citations
5. 05*

   Scalar production and decay to top quarks including interference effects at NLO in QCD in an EFT approach

   Diogo Buarque Franzosi🇩🇪 · Eleni Vryonidou🇳🇱 · Cen Zhang🇨🇳

   Scalar and pseudo-scalar resonances decaying to top quarks are common predictions in several scenarios beyond the standard model (SM) and are extensively searched for by LHC experiments. Challenges on the experimental side require optimising the strategy based on accurate predictions. Firstly, QCD corrections are known to be large both for the SM QCD background and for the pure signal scalar production. Secondly, leading order and approximate next-to-leading order (NLO) calculations indicate that the interference between signal and background is large and drastically changes the lineshape of the signal, from a simple peak to a peak-dip structure. Therefore, a robust prediction of this interference at NLO accuracy in QCD is necessary to ensure that higher-order corrections do not alter the lineshapes. We compute the exact NLO corrections, assuming a point-like coupling between the scalar and the gluons and consistently embedding the calculation in an effective field theory within an automated framework, and present results for a representative set of beyond the SM benchmarks. The results can be further matched to parton shower simulation, providing more realistic predictions. We find that NLO corrections are important and lead to a significant reduction of the uncertainties. We also discuss how our computation can be used to improve the predictions for physics scenarios where the gluon-scalar loop is resolved and the effective approach is less applicable.

   hep-phhep-exJHEP(2017)·33 citations
6. 06*

   On gauge dependence of gravitational waves from a first-order phase transition in classical scale-invariant $U(1{)}^{\prime }$ models

   Cheng-Wei Chiang🇹🇼 · Eibun Senaha🇹🇼

   We study gauge dependence of gravitational waves produced from a first-order phase transition in classical scale-invariant $U(1{)}^{\prime }$ models. Accidental gauge independence of the one-loop effective potential in this class of models is spoiled by including thermal resummation. The gauge artifact in the resummed effective potential propagates to the gravitational wave spectrum and results in one order of magnitude uncertainties in the prediction under a specific gauge choice.

   hep-phPLB(2017)·46 citations
7. 07*

   EDM with and beyond flavor invariants

   Christopher Smith🇫🇷 · Selim Touati🇫🇷

   In this paper, the flavor structure of quark and lepton EDMs in the SM and beyond is investigated using tools inspired from Minimal Flavor Violation. While Jarlskog-like flavor invariants are adequate for estimating CP-violation from closed fermion loops, non-invariant structures arise from rainbow-like processes. Our goal is to systematically construct these latter flavor structures in the quark and lepton sectors, assuming different mechanisms for generating neutrino masses. Numerically, they are found typically much larger, and not necessarily correlated with, Jarlskog-like invariants. Finally, the formalism is adapted to deal with a third class of flavor structures, sensitive to the flavored U(1) phases, and used to study the impact of the strong CP-violating interaction and the interplay between the neutrino Majorana phases and possible baryon and/or lepton number violating interactions.

   hep-phNPB(2017)·25 citations
8. 08*

   New insights into hadron production mechanism from $p_T$ spectra in $pp$ collisions at $\sqrt{s}=7$ TeV

   Xing-rui Gou🇨🇳 · Feng-lan Shao🇨🇳 · Rui-qin Wang🇨🇳 · Hai-hong Li🇨🇳 · Jun Song🇨🇳

   We show that the experimental data of mid-rapidity $p_T$ spectra for proton, $\Lambda$, $\Xi$ , ${\Omega }^{-}$, ${\text{K(892)}}^{\ast 0}$ and $\Xi (1530{)}^{\ast 0}$ in minimum-bias $pp$ collisions at $\sqrt{s}=7$ TeV can be systemically explained by the quark combination mechanism of hadronization. The averaged transverse momentum $⟨p_T⟩$ and spectra ratios such as $\Xi /\Lambda$ and $\Omega /\varphi$ calculated from quark combination reproduce the data much better than those from traditional string and/or cluster fragmentation. The available data of hadronic $p_T$ spectra released by ALICE collaboration in the first three high-multiplicity classes of $pp$ collisions at $\sqrt{s}=7$ TeV are also well explained. We make predictions for other hadrons, and propose two scaling behaviors among decuplet baryons and vector mesons as the effective probe of hadron production mechanism at such high collision energy.

   hep-phnucl-thPRD(2017)·22 citations
9. 09*

   Variational study of mass generation and deconfinement in Yang-Mills theory

   Giorgio Comitini🇮🇹 · Fabio Siringo🇮🇹

   A very simple variational approach to pure SU($N$) Yang-Mills theory is proposed, based on the Gaussian effective potential in a linear covariant gauge. The method provides an analytical variational argument for mass generation. The method can be improved order by order by a perturbative massive expansion around the optimal trial vacuum. At finite temperature, a weak first-order transition is found (at $T_c\approx 250$ MeV for $N=3$) where the mass scale drops discontinuously. Above the transition the optimal mass increases linearly as expected for deconfined bosons. The equation of state is found in good agreement with the lattice data.

   hep-phhep-lathep-thPRD(2018)·27 citations
10. 10*

    Fermionic bound states in Minkowski-space: Light-cone singularities and structure

    W. de Paula🇧🇷 · T. Frederico🇧🇷 · G. Salmè🇮🇹 · M. Viviani🇮🇹 · R. Pimentel🇧🇷

    The Bethe-Salpeter equation for two-body bound system with spin $1/2$ constituent is addressed directly in the Minkowski space. In order to accomplish this aim we use the Nakanishi integral representation of the Bethe-Salpeter amplitude and exploit the formal tool represented by the exact projection onto the null-plane. This formal step allows one i) to deal with end-point singularities one meets and ii) to find stable results, up to strongly relativistic regimes, that settles in strongly bound systems. We apply this technique to obtain the numerical dependence of the binding energies upon the coupling constants and the light-front amplitudes for a fermion-fermion $0^{+}$ state with interaction kernels, in ladder approximation, corresponding to scalar-, pseudoscalar- and vector boson exchanges, respectively. After completing the numerical survey of the previous cases, we extend our approach to a quark-antiquark system in $0^{-}$ state, taking both constituent-fermion and exchanged boson masses, from lattice calculations. Interestingly, the calculated light-front amplitudes for such a mock pion show peculiar signatures of the spin degrees of freedom.

    hep-phhep-lathep-thnucl-thEPJC(2017)·32 citations
11. 11*

    Analytical solution for the Zee mechanism

    A. C. B. Machado🇧🇷 · J. Montaño🇧🇷 · Pedro Pasquini🇧🇷 · V. Pleitez🇧🇷

    We found an analytical solution for the neutrino mass matrix in the most general case of the Zee model. Using the recent data on the neutrino parameters besides generating neutrino masses at 1-loop level we fit also the masses of the charged leptons and the leptonic mixing matrix. We also show in what conditions the model is not compatible with neutrino data.

    hep-ph6 citations
12. 12*

    DPS in CGC: Double Quark Production and Effects of Quantum Statistics

    Alex Kovner🇺🇸 · Amir H. Rezaeian🇨🇱

    We consider forward inclusive production of two quarks in the high energy p-A collisions in the CGC formalism. We demonstrate that the production cross-section is determined by the convolution of the proton generalized double transverse momentum-dependent distribution (2GTMD) functions with two independent eikonal scattering amplitudes: the product of two dipoles and a quadrupole. We explicitly demonstrate that the quadrupole amplitude term accounts for all the (initial and final state) effects of quantum statistics for identical fermions, and the correlations due to these effects. We also demonstrate that the effects due to quantum statistics (entirely encoded in the quadrupole) are parametrically leading contributions to the correlated particle production at large $N_c$. For non-identical quarks the quadrupole term also leads to correlated production which has characteristics similar to the HBT effect.

    hep-phhep-exnucl-exnucl-thPRD(2017)·33 citations
13. 13*

    From quarks to nucleons in dark matter direct detection

    Fady Bishara🇬🇧 · Joachim Brod🇩🇪 · Benjamin Grinstein🇺🇸 · Jure Zupan🇺🇸

    We provide expressions for the nonperturbative matching of the effective field theory describing dark matter interactions with quarks and gluons to the effective theory of nonrelativistic dark matter interacting with nonrelativistic nucleons. We give the leading and subleading order expressions in chiral counting. In general, a single partonic operator already matches onto several nonrelativistic operators at leading order in chiral counting. Thus, keeping only one operator at the time in the nonrelativistic effective theory does not properly describe the scattering in direct detection. Moreover, the matching of the axial--axial partonic level operator, as well as the matching of the operators coupling DM to the QCD anomaly term, naively include momentum suppressed terms. However, these are still of leading chiral order due to pion poles and can be numerically important. We illustrate the impact of these effects with several examples.

    hep-phastro-ph.COJHEP(2017)·165 citations
14. 14*

    Direct $CP$ Violation in $K\to {\mu }^{+}{\mu }^{-}$

    Giancarlo D'Ambrosio🇮🇹 · Teppei Kitahara🇩🇪

    A rare decay $K_L\to {\mu }^{+}{\mu }^{-}$ has been measured precisely, while a rare decay $K_S\to {\mu }^{+}{\mu }^{-}$ will be observed by an upgrade of the LHCb experiment. Although both processes are almost CP-conserving decays, we point out that an interference contribution between $K_L$ and $K_S$ in the kaon beam emerges from a genuine direct CP violation. It is found that the interference contribution can change $K_S\to {\mu }^{+}{\mu }^{-}$ standard-model predictions at $\mathcal{O}(60\%)$. We also stress that an unknown sign of $\mathcal{A}(K_L\to \gamma \gamma )$ can be determined by a measurement of the interference, which can much reduce a theoretical uncertainty of $\mathcal{B}(K_L\to {\mu }^{+}{\mu }^{-})$. We also investigate the interference in a new physics model, where the ${ϵ}_K^{\prime }/{ϵ}_K$ tension is explained by an additional $Z$-penguin contribution.

    hep-phhep-exPRL(2017)·92 citations
15. 15*

    LHC Dark Matter Signals from Vector Resonances and Top Partners

    Alexander S. Belyaev🇬🇧 · Thomas Flacke🇰🇷 · Bithika Jain🇧🇷 · Patrick B. Schaefers🇬🇧

    Extensions of the Standard Model which address the hierarchy problem and dark matter (DM) often contain top partners and additional resonances at the TeV scale. We explore the phenomenology of a simplified effective model with a vector resonance $Z^{\prime }$, a fermionic vector-like coloured partner of the top quark $T^{\prime }$ as well as a scalar DM candidate $\varphi$ and provide publicly available implementations in CalcHEP and MadGraph. We study the $pp\to Z^{\prime }\to T^{\prime }\overline{T^{\prime }}\to t\bar{t}\varphi \varphi$ process at the LHC and find that it plays an important role in addition to the $T^{\prime }\overline{T^{\prime }}$ production via strong interactions. It turns out that the presence of the $Z^{\prime }$ can provide a dominant contribution to the $t\bar{t}+E_T^{\text{miss}}$ signature without conflicting with existing bounds from $Z^{\prime }$ searches in di-jet and di-lepton final states. We find that through this process, the LHC is already probing DM masses up to about 900 GeV and top partner masses up to about 1.5 TeV, thus exceeding the current bounds from QCD production alone almost by a factor of two for both particles.

    hep-phPRD(2018)·2 citations
16. 16*

    Experimental evidence of radiation reaction in the collision of a high-intensity laser pulse with a laser-wakefield accelerated electron beam

    J. M. Cole · K. T. Behm · T. G. Blackburn · J. C. Wood · C. D. Baird · M. J. Duff · C. Harvey · A. Ilderton · A. S. Joglekar · K. Krushelnik · S. Kuschel · M. Marklund and 12 other authors

    The dynamics of energetic particles in strong electromagnetic fields can be heavily influenced by the energy loss arising from the emission of radiation during acceleration, known as radiation reaction. When interacting with a high-energy electron beam, today's lasers are sufficiently intense to explore the transition between the classical and quantum radiation reaction regimes. We report on the observation of radiation reaction in the collision of an ultra-relativistic electron beam generated by laser wakefield acceleration ($\epsilon >500$ MeV) with an intense laser pulse ($a_0>10$). We measure an energy loss in the post-collision electron spectrum that is correlated with the detected signal of hard photons ($\gamma$-rays), consistent with a quantum (stochastic) description of radiation reaction. The generated $\gamma$-rays have the highest energies yet reported from an all-optical inverse Compton scattering scheme, with critical energy ${\epsilon }_{\mathrm{crit}}>$ 30 MeV.

    ↳ physics.plasm-phhep-phPRX(2018)·386 citations
17. 17*

    Gauss-Bonnet-coupled Quintessential Inflation

    Carsten van de Bruck🇬🇧 · Konstantinos Dimopoulos🇬🇧 · Chris Longden🇬🇧 · Charlotte Owen🇬🇧

    We study in detail a new model of quintessential inflation where the inflaton field is coupled to the Gauss-Bonnet term. This coupling ensures that the variation of the field is kept sub-Planckian, which avoids the 5th force problem as well as the lifting of the flatness of the quintessential tail in the runaway scalar potential due to radiative corrections. We find that the inflationary predictions of the model are in excellent agreement with CMB observations, while the coincidence requirement of dark energy is satisfied with natural values of the parameters, overcoming thereby the extreme fine-tuning of the cosmological constant in $\Lambda$CDM.

    ↳ astro-ph.COgr-qchep-phhep-th72 citations
18. 18*

    Production and acceleration of antinuclei in supernova shockwaves

    Nicola Tomassetti🇮🇹 · Alberto Oliva🇪🇸

    We compute the energy spectra of antideuterons and antihelium in cosmic rays (CRs) in a scenario where hadronic interactions inside supernova remnants (SNRs) can produce a diffusively-shock-accelerated "source component" of secondary antinuclei. The key parameters that specify the SNR environment and the interstellar CR transport are tightly constrained with the new measurements provided by the AMS experiment on the B/C ratio and on the antiproton/proton ratio. The best-fit models obtained from the two ratios are found to be inconsistent with each other, as the antiproton/proton data require enhanced secondary production. Thus, we derive conservative (i.e., B/C-driven) and speculative (antiproton/proton-driven) upper limits to the SNR flux contributions for the d and He spectra spectra in CRs, along with their standard secondary component expected from CR collisions in the interstellar gas. We find that the source component of antinuclei can be appreciable at kinetic energies above a few ~10 GeV/n, but it is always sub-dominant below a few GeV/n, that is the energy window where dark matter (DM) annihilation signatures are expected to exceed the level of secondary production. We also find that the total (standard + SNR) flux of secondary antinuclei is tightly bounded by the data. Thus the presence of interaction processes inside SNRs does not critically affect the total background for DM searches.

    ↳ astro-ph.HEhep-phApJL(2017)·19 citations
19. 19*

    Solar and nuclear physics uncertainties in cosmic-ray propagation

    Nicola Tomassetti🇮🇹

    Recent data released by the AMS experiment on the primary spectra and secondary-to-primary ratios in cosmic rays (CRs) can pose tight constraints to astrophysical models of CR acceleration and transport in the Galaxy, thereby providing a robust baseline of the astrophysical background for dark matter search via antimatter. However, models of CR propagation are affected by other important sources of uncertainties, notably from solar modulation and nuclear fragmentation, that cannot be improved with the sole use of the AMS data. The present work is aimed at assessing these uncertainties and their relevance in the interpretation of the new AMS data on the boron-to-carbon (B/C) ratio. Uncertainties from solar modulation are estimated using improved models of CR transport in the Heliosphere constrained against various type of measurements: monthly-resolved CR data collected by balloon-born or space missions, interstellar flux data from the Voyager-1 spacecraft, and counting rates from ground-based neutron monitor detectors. Uncertainties from nuclear fragmentation are estimated using semiempirical cross-section formulae constrained by measurements on isotopically-resolved and charge-changing reactions. We found that a proper data-driven treatment of solar modulation can guarantee the desired level of precision, in comparison with the improved accuracy of the recent data on the B/C ratio. On the other hand, nuclear uncertainties represent a serious limiting factor over a wide energy range. We therefore stress the need for establishing a dedicated program of cross-section measurements at the $\mathcal{O}$(100 GeV) energy scale.

    ↳ astro-ph.HEhep-phPRD(2017)·56 citations
20. 20*

    Production of antimatter nuclei in Galactic cosmic rays

    Alberto Oliva🇪🇸 · Nicola Tomassetti🇮🇹 · Jie Feng🇺🇸

    Antimatter nuclei in cosmic rays (CRs) are a promising tool for the indirect detection of dark-matter annihilation signatures. However, the search of new-physics signals in CRs relies on our knowledge of the astrophysical antimatter background which, in turns, depends critically on the several fragmentation cross-sections that regulate production and destruction of antiparticles in the interstellar medium. In this work, we have re-evaluated the astrophysical background of CR antiproton, antineutron, and antihelium nuclei in Galactic CRs using improved calculations. The production cross-sections of individual antinucleons are constrained using updated calculations that make use of recent accelerator data. The production of antideuteron and antihelium nuclei is calculated using an improved model of nuclear coalescence that accounts for the asymmetry in antineutron and antiproton production. We discuss the cross-section induced uncertainties and show that they are dominating in comparison with other uncertainties of astrophysical origin.

    ↳ astro-ph.HEhep-phPoS(2018)·4 citations
21. 21*

    Secondary antinuclei from supernova remnants and background for dark matter searches

    Nicola Tomassetti🇮🇹 · Alberto Oliva🇪🇸

    We compute the spectra of cosmic-ray (CR) nuclei and antinuclei under a scenario where hadronic interaction processes inside supernova remnants (SNRs) can produce a diffusively-shock-accelerated "source component" of secondary particles. This scenario is able to explain the recent measurements reported by AMS on the antiproton/proton ratio, that is found to be remarkably constant at ~60-450 GeV of kinetic energy. However, as we will show, this explanation is ruled out by the new AMS data on the B/C ratio, which is found to decrease steadily up to TeV/n energies. With the constraints provided by the two ratios, we calculate conservative (B/C driven) and speculative (pbar/p driven) SNR-induced flux contribution for the spectra of antideuteron and antihelium in CRs, along with their standard secondary component expected from CR collisions in the interstellar gas. We found that the SNR component of anti-nuclei can be significantly large at high-energy, above a few ~10 GeV/n, but it is always sub-dominant at sub-GeV/n energies, that is, the energy region where dark-matter induced signals may exceed the standard astrophysical background. Furthermore, the total antinuclei flux from insterstellar spallation plus SNR-component is tightly bounded by the data, so that hadronic production in SNRs has a minor impact on the astrophysical background for dark matter searches.

    ↳ astro-ph.HEhep-phPoS(2018)·3 citations
22. 22*

    Refined Study of Isocurvature Fluctuations in the Curvaton Scenario

    Naoya Kitajima🇯🇵 · David Langlois🇫🇷 · Tomo Takahashi🇯🇵 · Shuichiro Yokoyama🇯🇵

    We revisit the generation of dark matter isocurvature perturbations in the curvaton model in greater detail, both analytically and numerically. As concrete examples, we investigate the cases of thermally decoupled dark matter and axionic dark matter. We show that the radiation produced by the decay of the curvaton, which has not been taken into account in previous analytical studies, can significantly affect the amplitude of isocurvature perturbations. In particular, we find that they are drastically suppressed even when the dark matter freeze-out (or the onset of the axion oscillations for axionic dark matter) occurs before the curvaton decays, provided the freeze-out takes place deep in the curvaton-dominated Universe. As a consequence, we show that the current observational isocurvature constraints on the curvaton parameters are not as severe as usually thought.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2017)·6 citations
23. 23*

    Transverse Momentum Distribution and Elliptic Flow of Charged Hadrons in $U$+$U$ collisions at $\sqrt{s_{NN}}=193$ GeV using HYDJET++

    Arpit Singh🇮🇳 · P. K. Srivastava🇮🇳 · O. S. K. Chaturvedi🇮🇳 · S. Ahmad🇮🇳 · B. K. Singh🇮🇳

    Recent experimental observations of the charged hadron properties in $U+U$ collisions at $193$ GeV contradict many of the theoretical models of particle production including two-component Monte Carlo Glauber model. The experimental results show a small correlation between the charged hadron properties and the initial geometrical configurations (e.g. body-body, tip-tip etc.) of $U+U$ collisions. In this article, we have modified the Monte Carlo HYDJET++ model to study the charged hadron production in $U+U$ collisions at $193$ GeV center-of-mass energy in tip-tip and body-body initial configurations. We have modified the hard as well as soft production processes to make this model suitable for $U+U$ collisions. We have calculated the pseudorapidity distribution, transverse momentum distribution and elliptic flow distribution of charged hadrons with different control parameters in various geometrical configurations possible for $U+U$ collision. We find that HYDJET++ model supports a small correlation between the various properties of charged hadrons and the initial geometrical configurations of $U+U$ collision. Further, the results obtained in modified HYDJET++ model regarding $d{n}_{ch}/d\eta$ and elliptic flow ($v_2$) suitably matches with the experimental data of $U+U$ collisions in minimum bias configuration.

    ↳ nucl-thhep-phEPJC(2018)·15 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.