Transverse energy and charged particle production in heavy-ion collisions: From RHIC to LHC

We study the charged particle and transverse energy production mechanism from AGS, SPS, RHIC to LHC energies in the framework of nucleon and quark participants. At RHIC and LHC energies, the number of nucleons-normalized charged particle and transverse energy density in pseudorapidity, which shows a monotonic rise with centrality, turns out to be an almost centrality independent scaling behaviour when normalized to the number of participant quarks. A universal function which is a combination of logarithmic and power-law, describes well the charged particle and transverse energy production both at nucleon and quark participant level for the whole range of collision energies. Energy dependent production mechanisms are discussed both for nucleonic and partonic level. Predictions are made for the pseudorapidity densities of transverse energy, charged particle multiplicity and their ratio (the barometric observable, $\frac{dE_{\rm{T}}/d\eta}{dN_{\rm{ch}}/d\eta} ~\equiv \frac{E_{\rm{T}}}{N_{\rm{ch}}}$) at mid-rapidity for Pb+Pb collisions at $\sqrt{s_{\rm{NN}}}=5.5$ TeV. A comparison with models based on gluon saturation and statistical hadron gas is made for the energy dependence of $\frac{E_{\rm{T}}}{N_{\rm{ch}}}$.Comment: 19 pages, 7 figure

Charged Particle and Photon Multiplicity, and Transverse Energy Production in High-Energy Heavy-Ion Collisions

We review the charged particle and photon multiplicity, and transverse energy production in heavy-ion collisions starting from few GeV to TeV energies. The experimental results of pseudorapidity distribution of charged particles and photons at different collision energies and centralities are discussed. We also discuss the hypothesis of limiting fragmentation and expansion dynamics using the Landau hydrodynamics and the underlying physics. Meanwhile, we present the estimation of initial energy density multiplied with formation time as a function of different collision energies and centralities. In the end, the transverse energy per charged particle in connection with the chemical freeze-out criteria is discussed. We invoke various models and phenomenological arguments to interpret and characterize the fireball created in heavy-ion collisions. This review overall provides a scope to understand the heavy-ion collision data and a possible formation of a deconfined phase of partons via the global observables like charged particles, photons and the transverse energy measurement.Comment: 27 pages, 43 figures, Invited Review for Advances in High Energy physics for Special Issue on "Global properties in High Energy Collisions

Effective-energy universality approach describing total multiplicity centrality dependence in heavy-ion collisions

The recently proposed participant dissipating effective-energy approach is applied to describe the dependence on centrality of the multiplicity of charged particles measured in heavy-ion collisions at the collision energies up to the highest LHC energy of 5 TeV. The effective-energy approach relates multihadron production in different types of collisions, by combining, under the proper collision energy scaling, the constituent quark picture with Landau relativistic hydrodynamics. The measurements are shown to be well described in terms of the centrality-dependent effective energy of participants and an explanation of the differences in the measurements at RHIC and LHC are given by means of the recently introduced hypothesis of the energy-balanced limiting fragmentation scaling. A similarity between the centrality data and the data from most central collisions is proposed pointing to the central character of participant interactions independent of centrality. The findings complement our recent investigations of the similar midrapidity pseudorapidity density measurements extending the description to the full pseudorapidity range in view of the considered similarity of multihadron production in nucleon interactions and heavy-ion collisions.Comment: Same as published versio

Effective-energy budget in multiparticle production in nuclear collisions

The dependencies of charged particle pseudorapidity density and transverse energy pseudorapidity density at midrapidity on the collision energy and on the number of nucleon participants, or centrality, measured in nucleus-nucleus collisions are studied in the energy range spanning a few GeV to a few TeV per nucleon. The model in which the multiparticle production is driven by the dissipating effective energy of participants is introduced. The model is based on the earlier proposed approach, combining the constituent quark picture together with Landau relativistic hydrodynamics shown to interrelate the measurements from different types of collisions. Within this model, the dependence on the number of participants in heavy-ion collisions are found to be well described in terms of the effective energy defined as a centrality-dependent fraction of the collision energy. For both variables under study, the effective energy approach reveals a similarity in the energy dependence obtained for the most central collisions and centrality data in the entire available energy range. Predictions are made for the investigated dependencies for the forthcoming higher energy measurements in heavy-ion collisions at the LHC.Comment: Regular article, Replaced with published versio

Ready-to-use post-Newtonian gravitational waveforms for binary black holes with non-precessing spins: An update

For black-hole binaries whose spins are (anti-) aligned with respect to the orbital angular momentum of the binary, we compute the frequency domain phasing coefficients including the quadratic-in-spin terms up to the third post-Newtonian (3PN) order, the cubic-in-spin terms at the leading order, 3.5PN, and the spin-orbit effects up to the 4PN order. In addition, we obtain the 2PN spin contributions to the amplitude of the frequency-domain gravitational waveforms for non-precessing binaries, using recently derived expressions for the time-domain polarization amplitudes of binaries with generic spins, complete at that accuracy level. These two results are updates to Arun et al. (2009) [1] for amplitude and Wade et al. (2013) [2] for phasing. They should be useful to construct banks of templates that model accurately non-precessing inspiraling binaries, for parameter estimation studies, and or constructing analytical template families that accounts for the inspiral-merger-ringdown phases of the binary.Comment: 8 pages, an additional file (readable in MATHEMATICA) containing all the key results included in the sourc

AlGaN /GaN superlattice based p-channel field effect transistor (pFET) with TMAH treatment

To realize the full spectrum of advantages that the III-nitride materials system offers, the demonstration of p-channel III-nitride based devices is valuable. Authors report the first p-type field effect transistor (pFET) based on an AlGaN/GaN superlattice (SL), grown using MOCVD. Magnesium was used as the p-type dopant. A sheet resistance of 11.6 k{\Omega}/sq, and a contact resistance of 14.9{\Omega}.mm was determined using transmission line measurements (TLM) for a Mg doping of 1.5e19cm^-3 of Mg. Mobilities in the range of 7-10 cm\^2/Vs and a total sheet charge density in the range of 1e13-6e13 cm-2 were measured using room temperature Hall effect measurements. Without Tetramethylammonium hydroxide (TMAH) treatment, the fabricated pFETs had a maximum drain-source current (IDS) of 3mA/mm and an On-Resistance (RON) of 3.48 k{\Omega}.mm, and did not turn-off completely. With TMAH treatment during fabrication, a maximum IDS of 4.5mA/mm, RON of 2.2k{\Omega}.mm, and five orders of current modulation was demonstrated, which is the highest achieved for a p-type transistor based on (Al,Ga)N.Comment: Submitted to PSS (a) under reveie

Energy and Centrality dependence of dNch/dηdN_{\rm ch}/d\eta and dET/dηdE_{\rm T}/d\eta in Heavy-Ion Collisions from sNN\sqrt{s_{\rm NN}} =7.7 GeV to 5.02 TeV

The centrality dependence of pseudorapidity density of charged particles and transverse energy is studied for a wide range of collision energies for heavy-ion collisions at midrapidity from 7.7 GeV to 5.02 TeV. A two-component model approach has been adopted to quantify the soft and hard components of particle production, coming from nucleon participants and binary nucleon-nucleon collisions, respectively. Within experimental uncertainties, the hard component contributing to the particle production has been found not to show any clear collision energy dependence from RHIC to LHC. The effect of centrality and collision energy in particle production seem to factor out with some degree of dependency on the collision species. The collision of Uranium-like deformed nuclei opens up new challenges in understanding the energy-centrality factorization, which is evident from the centrality dependence of transverse energy density, when compared to collision of symmetric nuclei.Comment: Published version in Eur. Phys. J.