The exploration of the phase diagram of Quantum ChromoDynamics (QCD) is
carried out by studying ultrarelativistic heavy-ion collisions. The energy
range covered by the CERN SPS ($\sqrt{s_{\rm ...\scriptscriptstyle{NN}}} \sim$
6-17 GeV) is ideal for the investigation of the region of the phase diagram
corresponding to finite baryochemical potential ($\mu_{\rm B}$), and has been
little explored up to now. We propose in this document a new experiment, NA60+,
that would address several observables which are fundamental for the
understanding of the phase transition from hadronic matter towards a
Quark-Gluon Plasma (QGP) at SPS energies. In particular, we propose to study,
as a function of the collision energy, the production of thermal dimuons from
the created system, from which one would obtain a caloric curve of the QCD
phase diagram that is sensitive to the order of the phase transition. In
addition, the measurement of a $\rho$-a$_1$ mixing contribution would provide
conclusive insights into the restoration of the chiral symmetry of QCD. In
parallel, studies of heavy quark and quarkonium production would also be
carried out, addressing the measurement of transport properties of the QGP and
the investigation of the onset of the deconfinement transition. The document
also defines an experimental set-up which couples a vertex telescope based on
monolithic active pixel sensors (MAPS) to a muon spectrometer with tracking
(GEM) and triggering (RPC) detectors within a large acceptance toroidal magnet.
Results of physics performance studies for most observables accessible to NA60+
are discussed, showing that the results of the experiment would lead to a
significant advance of our understanding of strong interaction physics. The
document has been submitted as an input to the European Particle Physics
Strategy Update 2018-2020 (http://europeanstrategyupdate.web.cern.ch/).
This document was prepared by the community that is active in Italy, within INFN (Istituto Nazionale di Fisica Nucleare), in the field of ultra-relativistic heavy-ion collisions. The experimental ...study of the phase diagram of strongly-interacting matter and of the Quark-Gluon Plasma (QGP) deconfined state will proceed, in the next 10-15 years, along two directions: the high-energy regime at RHIC and at the LHC, and the low-energy regime at FAIR, NICA, SPS and RHIC. The Italian community is strongly involved in the present and future programme of the ALICE experiment, the upgrade of which will open, in the 2020s, a new phase of high-precision characterisation of the QGP properties at the LHC. As a complement of this main activity, there is a growing interest in a possible future experiment at the SPS, which would target the search for the onset of deconfinement using dimuon measurements. On a longer timescale, the community looks with interest at the ongoing studies and discussions on a possible fixed-target programme using the LHC ion beams and on the Future Circular Collider.
The exploration of the phase diagram of Quantum ChromoDynamics (QCD) is carried out by studying ultrarelativistic heavy-ion collisions. The energy range covered by the CERN SPS (\(\sqrt{s_{\rm ...\scriptscriptstyle{NN}}} \sim\) 6-17 GeV) is ideal for the investigation of the region of the phase diagram corresponding to finite baryochemical potential (\(\mu_{\rm B}\)), and has been little explored up to now. We propose in this document a new experiment, NA60+, that would address several observables which are fundamental for the understanding of the phase transition from hadronic matter towards a Quark-Gluon Plasma (QGP) at SPS energies. In particular, we propose to study, as a function of the collision energy, the production of thermal dimuons from the created system, from which one would obtain a caloric curve of the QCD phase diagram that is sensitive to the order of the phase transition. In addition, the measurement of a \(\rho\)-a\(_1\) mixing contribution would provide conclusive insights into the restoration of the chiral symmetry of QCD. In parallel, studies of heavy quark and quarkonium production would also be carried out, addressing the measurement of transport properties of the QGP and the investigation of the onset of the deconfinement transition. The document also defines an experimental set-up which couples a vertex telescope based on monolithic active pixel sensors (MAPS) to a muon spectrometer with tracking (GEM) and triggering (RPC) detectors within a large acceptance toroidal magnet. Results of physics performance studies for most observables accessible to NA60+ are discussed, showing that the results of the experiment would lead to a significant advance of our understanding of strong interaction physics. The document has been submitted as an input to the European Particle Physics Strategy Update 2018-2020 (http://europeanstrategyupdate.web.cern.ch/).
Heavy quarks, like charm and beauty, are sensitive probes to investigate the colour-deconfined medium created in high-energy heavy-ion collisions, the Quark–Gluon Plasma (QGP). The ALICE ...Collaboration measured the production of D0, D+, D*+ and D+s in Pb–Pb collisions at sNN=5.02TeV. The measurement of the nuclear modification factor (RAA) provides information on the in-medium parton energy loss. In addition, the comparison between D+s and the non-strange D-meson RAA allows to investigate possible modifications of the charm-quark hadronisation mechanism in the QGP. The most recent results for these observables, which were obtained by analysing the latest 2018 data sample of Pb–Pb collisions as well as the comparison with theoretical model calculations, are presented.
Abstract
In ultra-relativistic heavy-ion collisions a great variety of (anti-)(hyper-)nuclei are produced, namely deuteron, triton,
3
He,
4
He, hypertriton (
Λ
3
H
) and their antiparticles. The ...ALICE experiment is the most suited to investigate the production of (hyper-)nuclei at the LHC, thanks to an excellent particle identification and low-material budget detectors. Recent results on (hyper-)nuclei production as a function of transverse momentum (
p
T) and charged particle multiplicity (d
N
ch
/d
η
) in Pb–Pb collisions are presented. The evolution of the production yields with the system size is also shown, via comparison to the results obtained in small collision systems, like pp and p–Pb. The results on the production of (hyper-)nuclei are also compared with the predictions based on a naive coalescence approach and the statistical hadronization models.
Furthermore, the latest and currently most precise measurement of the hypertriton lifetime is presented. It is compared with results obtained by different experimental techniques and with theoretical predictions.
The high collision energies reached at the LHC open the possibility to study extensively the production of light (anti-)(hyper-)nuclei and exotic bound states in proton-proton (pp), proton-lead ...(p-Pb) and lead-lead (Pb-Pb) collisions. ALICE has excellent particle identification (PID) capability which allows the detection of these rarely produced particles. PID is perfomed using several techniques, namely by exploiting the measurement of the specific ionization energy loss in the Time Projection Chamber (TPC) and the information of the Time-Of-Flight (TOF) detector. The transverse momentum spectra and the yields (dN/dy) of light nuclei and anti-nuclei were obtained and results are discussed here, and the first measurement of deuteron elliptic flow is presented. Furthermore, the study of the production of (anti-)hypertriton and the status of the searches for exotic bound states, i.e. Λ-Λ and Λ-n, are discussed. Results are compared to predictions from thermal and coalescence models in order to enquire into the production mechanisms of nuclei, hypernuclei and exotic bound states.
The formation and further reactions of halamines during oxidative water treatment can be relevant for water quality. In this study, we investigated the formation and reactivity of several inorganic ...and organic halamines (monochloramine, N-chloromethylamine, N-chlorodimethylamine, monobromamine, dibromamine, N-bromomethylamine, N,N-dibromomethylamine, and N-bromodimethylamine) by kinetic experiments, transformation product analysis, and quantum chemical computations. Kinetic model simulations were conducted to evaluate the relevance of halamines for various water treatment scenarios. Halamines were quickly formed from the reaction of chlorine and bromine with ammonia or organic amines. Species-specific second-order rate constants for the reaction of chlorine and bromine with ammonia, methyl- and dimethylamine were in the order of 106-108 M−1s−1. The formed halamines were found to be reactive towards phenolic compounds, forming halogenated phenols via electrophilic aromatic substitution (phenol and resorcinol) or quinones via electron transfer (catechol and hydroquinone). At near neutral pH, apparent second-order rate constants for these reactions were in the order of 10−4-10−1 M−1s−1 for chloramines and 101-102 M−1s−1 for bromamines. Quantum chemical computations were used to determine previously unknown aqueous pKa values, gas phase bond dissociation energies (BDE) and partial atomic charges of the halamines, allowing a better understanding of their reactivities. Kinetic model simulations, based on the results of this study, showed that during chlorination inorganic and organic chloramines are the main halamines formed. However, their further reactions with organic matter are outcompeted kinetically by chlorine. During ozonation, mainly inorganic bromamines are formed, since ozone quickly oxidizes organic amines. The further reactions of bromamine are typically outcompeted by ozone and thus generally of minor importance. The use of peracetic acid for saline ballast water treatment can result in the formation of substantial amounts of bromamines, which can react with dissolved organic matter and contribute to the formation of brominated products.
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•Novel rate constants for the formation and reactivity of several halamine species.•Second-order rate constants for halamine formation are 106–108 M−1 s−1.•Reactivity of bromamines with phenol is 102–106 times higher than for chloramines.•Reactivity of halamines can be linked to their physical-chemical properties.•Model calculations show the relevance of halamines during oxidative treatment.
The stabilities and speciation of the halamines in water are difficult to characterize experimentally. We provide theoretical estimates of aqueous standard free energies of formation for inorganic ...chloramines, bromamines, and bromochloramines, based on high-accuracy theoretical standard free energies of formation in gas phase combined with quantum chemical estimates of Henry’s law constant. Based on comparisons between several theoretical and experimental datasets, we assign an error of 1.1–1.2 log unit for equilibrium constants of several reactions leading to halamines in water. The reactions of ammonia with HOCl or HOBr that lead to dichloramine, trichloramine, and tribromamine are found to be thermodynamically more favorable than was previously believed. The newly reported equilibrium data also allow us to propose rate constant values for some hydrolysis and disproportionation reactions of dichloramine, monobromamine, and bromochloramine. Finally, theoretical results indicate aqueous acid dissociation constant (pK a) values of 1.5 ± 1 for NH3Cl+, 0.8 ± 1 for NH3Br+, 11.8 ± 1 for NHCl2, and 12.5 ± 1 for NHBrCl. The present report provides a comprehensive data set describing the free energies of the neutral inorganic halamines, the anionic conjugate base species, and the cationic conjugate acid species, with approximately uniform uncertainty bounds assigned throughout.
In this paper, we perform a dynamical study of the population of Hungaria asteroids, close to the exterior 2:3 mean-motion resonance (MMR) with Mars. The aim of this work is to initiate a catalog of ...asteroids captured in mean-motion resonances (MMRs) with Mars in the Hungaria region, by first identifying the minor bodies affected by the 2:3 MMR. To achieve our goal, we follow the temporal evolution of massless test particles by 2 Myr in the proximity of the 2:3 resonance considering the gravitational influence of all planets of the Solar System. We present a semi-analytical model to calculate the extension of the resonant region for a population with the dynamical characteristics of the Hungaria asteroids. We show that the resonance can disturb the asteroids in two ways: by capture or by indirect influence. We find 22 asteroids captured inside the 2:3 MMR and 89 asteroids which exhibit temporary librations around this resonance. The predictions of our model are in good agreement with the numerical results, which make it useful for the study of other MMRs in this region. For asteroids without determined synthetic proper elements, we use the results of our numerical simulations to calculate the mean orbital elements, which can be used as a first approximation of the proper elements.
•Long-term evolution is important to consider the effects of the planetary system.•A new dynamical model is needed for the analysis of asteroids with inclined orbits.•A classification of the population can improve the dynamical studies in the region.
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