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Jet production in charged-current deep-inelastic scattering to third order in QCD
http://cds.cern.ch/record/2652279
The production of jets in charged-current deep-inelastic scattering (CC DIS) probes simultaneously the strong and the electroweak sectors of the Standard Model; its measurement provides important information on the quark flavour structure of the proton. We compute third-order (N3LO) perturbative QCD corrections to this process, fully differential in the jet and lepton kinematics. We observe a substantial reduction in the theory uncertainty, to sub-percent level throughout the relevant kinematical range, thus enabling precision phenomenology with jet observables.Gehrmann, T.Niehues, J.Huss, A.Vogt, A.Walker, D.M.Wed, 19 Dec 2018 04:15:54 GMT2018-12-14CERN-TH-2018-272http://cds.cern.ch/record/26522792018272Polarized backgrounds of relic gravitons
http://cds.cern.ch/record/2652185
The polarizations of the tensor modes of the geometry evolving in cosmological backgrounds are treated as the components of a bispinor whose dynamics follows from an appropriate gauge-invariant action. This novel framework bears a close analogy with the (optical) Jones calculus and leads to a compact classification of the various interactions able to polarize the relic gravitons.Giovannini, MassimoTue, 18 Dec 2018 03:03:07 GMT2018-12-13CERN-TH-2018-215http://cds.cern.ch/record/26521852018215Collectivity in pp from resummed interference effects?
http://cds.cern.ch/record/2651074
Azimuthal asymmetries $v_n$ in the soft transverse momentum spectra of hadronic collisions can result as a consequence of quantum interference and color flow which translates spatial anisotropies into momentum anisotropies via multipole radiation patterns. Here, we analyze to what extent these effects result in signal strengths $v_n\lbrace 2s\rbrace$ that can persist in higher order $(2s)$ cumulants. In a simple model of soft multi-particle production with quantum interference effects in which $m$ particles are emitted from $N$ sources and in which interference contributions appear naturally ordered in inverse powers of the adjoint color trace, $1/(N_c^2-1)$, we provide the first resummed calculation of all powers of $m^2/(N_c^2-1)$. This allows one to determine all higher order flow cumulants $v_n\lbrace 2s\rbrace$ with the same parametric accuracy. For a phenomenologically relevant range of $N$ sources emitting $m$ particles, we find that the even flow coefficients $v_n\lbrace 2s\rbrace$ decrease very mildly with increasing cumulants. This provides a proof of principle that non-vanishing higher order cumulants $v_n\lbrace 2s\rbrace$ can persist in systems that exhibit neither final state interactions nor phenomena related to high (saturated) initial parton densities.Blok, BorisWiedemann, Urs AchimThu, 13 Dec 2018 03:57:15 GMT2018-12-10arXiv:1812.04113http://cds.cern.ch/record/2651074['arXiv:1812.04113']arXiv:1812.04113Two-dimensional fluids and their holographic duals
http://cds.cern.ch/record/2651073
We describe the dynamics of two-dimensional relativistic and Carrollian fluids. These are mapped holographically to three-dimensional locally anti-de Sitter and locally Minkowski spacetimes, respectively. To this end, we use Eddington-Finkelstein coordinates, and grant general curved two-dimensional geometries as hosts for hydrodynamics. This requires to handle the conformal anomaly, and the expressions obtained for the reconstructed bulk metrics incorporate non-conformal-fluid data. We also analyze the freedom of choosing arbitrarily the hydrodynamic frame for the description of relativistic fluids. This freedom breaks down in the dual gravitational picture, and fluid/gravity correspondence turns out to be sensitive to dissipation processes: the fluid heat current is a necessary ingredient for reconstructing all Banados asymptotically anti-de Sitter solutions. The same feature emerges for Carrollian fluids, which enjoy a residual frame invariance, and their Barnich-Troessaert locally Minkowski duals. These statements are proven by computing the algebra of surface conserved charges in the fluid-reconstructed bulk three-dimensional spacetimes.Campoleoni, AndreaCiambelli, LucaMarteau, CharlesPetropoulos, P. MariosSiampos, KonstantinosThu, 13 Dec 2018 03:57:14 GMT2018-12-10arXiv:1812.04019http://cds.cern.ch/record/2651073['arXiv:1812.04019']arXiv:1812.04019Observation angles, Fermi coordinates, and the Geodesic-Light-Cone gauge
http://cds.cern.ch/record/2650953
We show that the angular directions locally measured by a static geodesic observer in a generic cosmological background and expressed in the system of Fermi Normal Coordinates always coincide with those expressed in the Geodesic-Light-Cone (GLC) gauge, up to a local transformation which exploits the residual gauge freedom of the GLC coordinates. This is not the case for other gauges - like, for instance, the synchronous and longitudinal gauge - commonly used in the context of observational cosmology. We also make an explicit proposal for the GLC gauge-fixing condition that ensures a full identification of its angles with the observational ones.Fanizza, GiuseppeGasperini, MaurizioMarozzi, GiovanniVeneziano, GabrieleWed, 12 Dec 2018 03:03:39 GMT2018-12-10arXiv:1812.03671http://cds.cern.ch/record/2650953['arXiv:1812.03671']arXiv:1812.03671A Fresh Look at the Calculation of Tunneling Actions in Multi-Field Potentials
http://cds.cern.ch/record/2650777
The quantum decay of a metastable vacuum is exponentially suppressed by a tunneling action that can be calculated in the semi-classical approximation as the Euclidean action of a bounce that interpolates between the false and true phases. For multi-field potentials, finding the bounce is non-trivial due to its peculiar boundary conditions and the fact that the action at the bounce is not a minimum but merely a saddle point. Recently, an alternative tunneling action has been proposed that does not rely on Euclidean bounces and reproduces the standard result at its minimum. Here we generalize this new approach for several scalar fields and demonstrate how its use can significantly improve the numerical calculation of tunneling actions for multi-field potentials.Espinosa, J.R.Konstandin, T.Tue, 11 Dec 2018 03:09:49 GMT2018-11-22arXiv:1811.09185http://cds.cern.ch/record/2650777['arXiv:1811.09185']arXiv:1811.09185A General Classification of Starobinsky-like Inflationary Avatars of SU(2,1)/SU(2) x U(1) No-Scale Supergravity
http://cds.cern.ch/record/2650544
Measurements of the cosmic microwave background (CMB) favour models of inflation with a small tensor-to-scalar ratio r, as predicted by the Starobinsky R + R^2 model. It has been shown previously that various models based on no-scale supergravity with different forms of superpotential make predictions similar to those of the Starobinsky model. In this paper we present a unified and general treatment of Starobinsky avatars of no-scale supergravity, using the underlying non-compact SU(2,1)/SU(2) x U(1) symmetry to demonstrate equivalences between different models, exhibiting 6 specific equivalence classes.Ellis, JohnNanopoulos, Dimitri V.Olive, Keith A.Verner, SarunasSun, 09 Dec 2018 03:45:57 GMT2018-12-05arXiv:1812.02192http://cds.cern.ch/record/2650544['arXiv:1812.02192']arXiv:1812.02192Formation and Evolution of Primordial Black Hole Binaries in the Early Universe
http://cds.cern.ch/record/2650543
The abundance of primordial black holes (PBHs) in the mass range $0.1 - 10^3 M_\odot$ can potentially be tested by gravitational wave observations due to the large merger rate of PBH binaries formed in the early universe. To put the estimates of the latter on a firmer footing, we first derive analytical PBH merger rate for the general mass function considering only initial configurations that give a conservative result. We then study the formation and evolution of PBH binaries before recombination by performing N-body simulations. We find that the analytical merger rate estimate based on the tidally perturbed 2-body problem fails when PBHs comprise all dark matter, as most initial binaries are disrupted by the surrounding PBHs. This is due to the formation of compact N-body systems at matter-radiation equality. However, if PBHs make up a small fraction of the dark matter, $f_{\rm PBH} \lesssim 10\%$, these estimates become more reliable. In that case, the merger rate observed by LIGO imposes the strongest constraint on the PBH abundance in the mass range $2 - 160 M_\odot$. Finally, we argue that, even if most initial PBH binaries are perturbed, the present BH-BH merger rate of binaries formed in the early universe is larger than $\mathcal{O}(10)\,{\rm Gpc}^{-3} {\rm yr}^{-1}\, f_{\rm PBH}^3$.Raidal, MarttiSpethmann, ChristianVaskonen, VilleVeermäe, HardiSun, 09 Dec 2018 03:45:44 GMT2018-12-05arXiv:1812.01930http://cds.cern.ch/record/2650543['arXiv:1812.01930']arXiv:1812.01930Fermion-boson symmetry and quantum field theory
http://cds.cern.ch/record/2650542
The application of fermion-boson symmetry to the standard model leads to the following: first, there are three generations of scalar quarks and scalar leptons in addition to the known quarks and leptons, and, secondly, the divergences in the perturbation series for the standard model are reduced. In the light of experimental data from LEP, Tevatron Collider, and LHC, some consequences of these two statements taken together are discussed. A series of experiments are proposed to search for the scalar quarks and scalar leptons at the Large Hadron Collider. The first step in this search is to look for new fermions by analyzing events with a pair of oppositely changed leptons both with large transverse momenta. The scalar quarks and the scalar leptons are then searched for through their decays into these new fermions plus a known quark or lepton.Wu, Sau LanWu, Tai TsunZhou, ChenSun, 09 Dec 2018 03:45:44 GMT2018-11-30arXiv:1812.01988http://cds.cern.ch/record/2650542['arXiv:1812.01988']arXiv:1812.01988The CLIC Potential for New Physics
http://cds.cern.ch/record/2650541
The Compact Linear Collider (CLIC) is a mature option for the future of high energy physics. It combines the benefits of the clean environment of $e^+e^-$ colliders with operation at high centre-of-mass energies, allowing to probe scales beyond the reach of the Large Hadron Collider (LHC) for many scenarios of new physics. This places the CLIC project at a privileged spot in between the precision and energy frontiers, with capabilities that will significantly extend knowledge on both fronts at the end of the LHC era. In this report we review and revisit the potential of CLIC to search, directly and indirectly, for physics beyond the Standard Model.de Blas, J.Franceschini, R.Riva, F.Roloff, P.Schnoor, U.Spannowsky, M.Wells, J.D.Wulzer, A.Zupan, J.Alipour-Fard, S.Altmannshofer, W.Azatov, A.Azevedo, D.Baglio, J.Bauer, M.Bishara, F.Blaising, J.-J.Brass, S.Buttazzo, D.Chacko, Z.Craig, N.Cui, Y.Dercks, D.Di Luzio, L.Di Vita, S.Durieux, G.Fan, J.Ferreira, P.Frugiuele, C.Fuchs, E.García, I.Ghezzi, M.Greljo, A.Gröber, R.Grojean, C.Gu, J.Hunter, R.Joglekar, A.Kalinowski, J.Kilian, W.Kilic, C.Kotlarski, W.Kucharczyk, M.Leogrande, E.Linssen, L.Liu, D.Liu, Z.Lombardo, D.M.Low, I.Matsedonskyi, O.Marzocca, D.Mimasu, K.Mitov, A.Mitra, M.Moortgat-Pick, G.Mühlleitner, M.Najjari, S.Nardecchia, M.Neubert, M.No, J.M.Panico, G.Panizzi, L.Paul, A.Perelló, M.Perez, G.Plascencia, A.D.Pruna, G.M.Redigolo, D.Reece, M.Reuter, J.Riembau, M.Robens, T.Robson, A.Rolbiecki, K.Sailer, A.Sakurai, K.Sala, F.Santos, R.Schlaffer, M.Shim, S.Y.Shuve, B.Simoniello, R.Sokołowska, D.Ström, R.Tait, T.M.P.Tesi, A.Thamm, A.van der Kolk, N.Vantalon, T.Verhaaren, C.B.Vos, M.Watson, N.Weiland, C.Winter, A.Wittbrodt, J.Wojton, T.Xu, B.Yin, Z.Żarnecki, A.F.Zhang, C.Sun, 09 Dec 2018 03:45:41 GMT2018-12-05arXiv:1812.02093http://cds.cern.ch/record/2650541['arXiv:1812.02093']arXiv:1812.02093Topological susceptibility at $T>T_{\rm c}$ from master-field simulations of the SU(3) gauge theory
http://cds.cern.ch/record/2650537
The topological susceptibility is computed in the SU(3) gauge theory at temperatures $T$ above the critical temperature $T_{\rm c}$ using master-field simulations of very large lattices, where the infamous topology-freezing issue is effectively bypassed. Up to $T=2.0\,T_{\rm c}$ no unusually large lattice effects are observed and the results obtained in the continuum limit confirm the expected rapid decay of the susceptibility with increasing temperature. As a byproduct, the reference gradient-flow time $t_0$ is determined in the range of lattice spacings from $0.023$ to $0.1\,{\rm fm}$ with a precision of 2 per mille.Giusti, LeonardoLüscher, MartinSun, 09 Dec 2018 03:45:18 GMT2018-12-05arXiv:1812.02062http://cds.cern.ch/record/2650537['arXiv:1812.02062']arXiv:1812.02062Muon g-2 and implications for SUSY GUTs
http://cds.cern.ch/record/2650261
Nath, PFri, 07 Dec 2018 09:51:14 GMT2001-05http://cds.cern.ch/record/2650261['']Further refining the de Sitter swampland conjecture
http://cds.cern.ch/record/2650221
We propose an alternative refined de Sitter conjecture. It is given by a natural condition on a combination of the first and second derivatives of the scalar potential. We derive our conjecture in the same weak coupling, semi-classical regime where the previous refined de Sitter conjecture was derived, using the same tools together with a few more assumptions that we discuss. We further test and constrain free parameters in our conjecture using data points of a classical type IIA supergravity setup. Interestingly, our conjecture easily accommodates slow-roll single field inflation with a concave potential, favored by observations. The standard quintessence potential is in tension with our new conjecture, and we thus propose a different type of quintessence model.Andriot, DavidRoupec, ChristophFri, 07 Dec 2018 04:30:38 GMT2018-11-21arXiv:1811.08889http://cds.cern.ch/record/2650221['arXiv:1811.08889']arXiv:1811.08889A heuristic study of the distribution of primes in short and not-so-short intervals
http://cds.cern.ch/record/2649937
A numerical study on the distributions of primes in short intervals of length
$h$ over the natural numbers $N$ is presented. Based on Cram\'er's model in
Number Theory, we obtain a heuristic expression applicable when $h \gg \log{N}$
but $h \ll N$, providing support to the Montgomery and Soundararajan conjecture
on the variance of the prime distribution at this scale.Sanchis-Lozano, Miguel-AngelWed, 05 Dec 2018 03:14:44 GMT2018-04-20CERN-TH-2018-83http://cds.cern.ch/record/2649937201883Three Neutrino Oscillations in Uniform Matter
http://cds.cern.ch/record/2649936
Following similar approaches in the past, the Schrodinger equation for three neutrino propagation in matter of constant density is solved analytically by two successive diagonalizations of 2x2 matrices. The final result for the oscillation probabilities is obtained directly in the conventional parametric form as in the vacuum but with explicit simple modification of two mixing angles ($\theta_{12}$ and $\theta_{13}$) and mass eigenvalues.Ioannisian, AraPokorski, StefanWed, 05 Dec 2018 03:14:43 GMT2018-12-03arXiv:1812.00701http://cds.cern.ch/record/2649936['arXiv:1812.00701']arXiv:1812.00701Dark matter and the early Universe
http://cds.cern.ch/record/2649802
Big-Bang nucleosynthesis (BBN) represents one of the earliest phenomena that can lead to observational constraints on the early Universe properties. It is well-known that many important mechanisms and phase transitions occurred before BBN. We discuss the possibility of gaining insight into the primordial Universe through studies of dark matter in cosmology, astroparticle physics and colliders. For this purpose, we assume that dark matter is a thermal relic, and show that combining collider searches with dark matter observables can lead to strong constraints on the period of freeze-out before BBN.Arbey, A.Ellis, J.Mahmoudi, F.Robbins, G.Tue, 04 Dec 2018 04:04:50 GMT2018-11-30arXiv:1811.12764http://cds.cern.ch/record/2649802['arXiv:1811.12764']arXiv:1811.12764Status of the (p)MSSM Higgs sector
http://cds.cern.ch/record/2649801
We present some highlights on the complementaries of the Higgs and SUSY searches at the LHC, using the 8 and 13 TeV results. In particular, we discuss the constraints that can be obtained on the MSSM parameters by the determination of the Higgs boson mass and couplings. In addition, we investigate the interplay with heavy Higgs searches, and evaluate how higher LHC luminosities and a future linear collider can help probing the pMSSM Higgs sector and reconstructing the underlying parameters.Arbey, A.Battaglia, M.Djouadi, A.Mahmoudi, F.Mühlleitner, M.Robbins, G.Spira, M.Tue, 04 Dec 2018 04:04:49 GMT2018-11-30arXiv:1811.12765http://cds.cern.ch/record/2649801['arXiv:1811.12765']arXiv:1811.12765SuperIso Relic new extensions for direct and indirect detection
http://cds.cern.ch/record/2649800
SuperIso Relic is a public computing program for the calculation of flavour observables and relic density in supersymmetry (MSSM and NMSSM). We present new extensions of the code dedicated to the calculation of dark matter direct and indirect detection constraints from the latest experimental results. Contrary to most of the existing programs, this new version allows the user to consider straightforwardly the uncertainties related to nuclear form factors, dark matter density and velocity, as well as cosmic-ray propagation through the galactic medium. The user thus finds a direct way to calculate "conservative", "standard" or "stringent" constraints according to the chosen set of uncertainties. Some examplified results showing the impact of such uncertainties are also presented.Robbins, G.Arbey, A.Mahmoudi, F.Tue, 04 Dec 2018 04:04:46 GMT2018-11-30arXiv:1811.12736http://cds.cern.ch/record/2649800['arXiv:1811.12736']arXiv:1811.12736Probing the scalar potential via double Higgs boson production at hadron colliders
http://cds.cern.ch/record/2649527
We present a sensitivity study on the cubic and quartic self couplings in double Higgs production via gluon fusion at hadron colliders. Considering the relevant operators in the Standard Model Effective Field Theory up to dimension eight, we calculate the dominant contributions up to two-loop level, where the first dependence on the quartic interaction appears. Our approach allows to study the independent variations of the two self couplings and to clearly identify the terms necessary to satisfy gauge invariance and to obtain UV-finite results order by order in perturbation theory. We focus on the $b \bar b \gamma \gamma$ signature for simplicity and provide the expected bounds for the cubic and quartic self couplings at the 14 TeV LHC with 3000 fb$^{-1}$ (HL-LHC) and for a future 100 TeV collider (FCC-100) with 30 ab$^{-1}$. We find that while the HL-LHC will provide very limited sensitivity on the quartic self coupling, precision measurements of double Higgs production at a FCC-100 will offer the opportunity to set competitive bounds. We show that combining information from double and triple Higgs production leads to significantly improved prospects for the determination of the quartic self coupling.Borowka, SophiaDuhr, ClaudeMaltoni, FabioPagani, DavideShivaji, AmbreshZhao, XiaoranSat, 01 Dec 2018 03:45:11 GMT2018-11-29arXiv:1811.12366http://cds.cern.ch/record/2649527['arXiv:1811.12366']arXiv:1811.12366Lower limit on the entropy of black holes as inferred from gravitational wave observations
http://cds.cern.ch/record/2649526
Black hole (BH) thermodynamics was established by Bekenstein and Hawking, who made abstract theoretical arguments about the second law of thermodynamics and quantum theory in curved spacetime respectively. Testing these ideas experimentally has, so far, been impractical because the putative flux of Hawking radiation from astrophysical BHs is too small to be distinguished from the rest of the hot environment. Here, it is proposed that the spectrum of emitted gravitational waves (GWs) after the merger of two BHs, in particular the spectrum of GW150914, can be used to infer a lower limit on the magnitude of the entropy of the post-merger BH. This lower bound is significant as it is the same order as the Bekenstein-Hawking entropy. To infer this limit, we first assume that the result of the merger is an ultracompact object with an external geometry which is Schwarzschild or Kerr, but with an outer surface which is capable of reflecting in-falling GWs rather than fully absorbing them. Because of the absence of deviations from the predictions of general relativity in detected GW signals, we then obtain a bound on the minimal redshift factor of GWs that emerge from the vicinity of the object's surface. The lack of deviations also means that the merger remnant essentially needs to have an absorbing surface, and thus it must effectively be a BH. Finally, a relationship between the minimal redshift factor and the BH entropy, which was first proposed by 't Hooft, is used to set a lower bound on the entropy of the post-merger BH.Brustein, RamMedved, A.J.M.Yagi, K.Sat, 01 Dec 2018 03:45:11 GMT2018-11-29arXiv:1811.12283http://cds.cern.ch/record/2649526['arXiv:1811.12283']arXiv:1811.12283Universal Relations in Composite Higgs Models
http://cds.cern.ch/record/2649520
We initiate a phenomenological study of `universal relations' in composite Higgs models, which are dictated by nonlinear shift symmetries acting on the 125 GeV Higgs boson. These are relations among one Higgs couplings with two electroweak gauge bosons (HVV), two Higgses couplings with two electroweak gauge bosons (HHVV), one Higgs couplings with three electroweak gauge bosons (HVVV), as well as triple gauge boson couplings (TGC), which are all controlled by a single input parameter: the decay constant $f$ of the pseudo-Nambu-Goldstone Higgs boson. Assuming custodial invariance in strong sector, the relation is independent of the symmetry breaking pattern in the UV, for an arbitrary symmetric coset $G/H$. The complete list of corrections to HVV, HHVV, HVVV and TGC couplings in composite Higgs models is presented to all orders in $1/f$, and up to four-derivative level, without referring to a particular $G/H$. We then present several examples of universal relations in ratios of coefficients which could be extracted experimentally. Measuring the universal relation requires a precision sensitive to effects of dimension-8 operators in the effective Lagrangian and highlights the importance of verifying the tensor structure of HHVV interactions in the standard model, which remains untested to date.Liu, DaLow, IanYin, ZheweiSat, 01 Dec 2018 03:44:46 GMT2018-09-24arXiv:1809.09126http://cds.cern.ch/record/2649520['arXiv:1809.09126']arXiv:1809.09126A GPU compatible quasi-Monte Carlo integrator interfaced to pySecDec
http://cds.cern.ch/record/2649399
The purely numerical evaluation of multi-loop integrals and amplitudes can be a viable alternative to analytic approaches, in particular in the presence of several mass scales, provided sufficient accuracy can be achieved in an acceptable amount of time. For many multi-loop integrals, the fraction of time required to perform the numerical integration is significant and it is therefore beneficial to have efficient and well-implemented numerical integration methods. With this goal in mind, we present a new stand-alone integrator based on the use of (quasi-Monte Carlo) rank-1 shifted lattice rules. For integrals with high variance we also implement a variance reduction algorithm based on fitting a smooth function to the inverse cumulative distribution function of the integrand dimension-by-dimension. Additionally, the new integrator is interfaced to pySecDec to allow the straightforward evaluation of multi-loop integrals and dimensionally regulated parameter integrals. In order to make use of recent advances in parallel computing hardware, our integrator can be used both on CPUs and CUDA compatible GPUs where available.Borowka, S.Heinrich, G.Jahn, S.Jones, S.P.Kerner, M.Schlenk, J.Fri, 30 Nov 2018 03:16:27 GMT2018-11-28arXiv:1811.11720http://cds.cern.ch/record/2649399['arXiv:1811.11720']arXiv:1811.11720Dark, Cold, and Noisy: Constraining Secluded Hidden Sectors with Gravitational Waves
http://cds.cern.ch/record/2649398
We explore gravitational wave signals arising from first-order phase transitions occurring in a secluded hidden sector, allowing for the possibility that the hidden sector may have a different temperature than the Standard Model sector. We present the sensitivity to such scenarios for both current and future gravitational wave detectors in a model-independent fashion. Since secluded hidden sectors are of particular interest for dark matter models at the MeV scale or below, we pay special attention to the reach of pulsar timing arrays. Cosmological constraints on light degrees of freedom restrict the number of sub-MeV particles in a hidden sector, as well as the hidden sector temperature. Nevertheless, we find that observable first-order phase transitions can occur. To illustrate our results, we consider two minimal benchmark models: a model with two gauge singlet scalars and a model with a spontaneously broken $U(1)$ gauge symmetry in the hidden sector.Breitbach, MoritzKopp, JoachimMadge, EricOpferkuch, TobySchwaller, PedroFri, 30 Nov 2018 03:16:24 GMT2018-11-27arXiv:1811.11175http://cds.cern.ch/record/2649398['arXiv:1811.11175']arXiv:1811.11175Chemical equilibration in weakly coupled QCD
http://cds.cern.ch/record/2649391
We study thermalization, hydrodynamization, and chemical equilibration in out-of-equilibrium Quark-Gluon Plasma starting from various initial conditions using QCD effective kinetic theory, valid at weak coupling. In non-expanding systems gauge bosons rapidly lose information of initial state and achieve kinetic equilibrium among themselves, while fermions approach the equilibrium distribution only at later time. In systems undergoing rapid longitudinal expansion, both gluons and quarks are kept away from equilibrium by the expansion, but the evolution is well described by fluid dynamics even before local thermal equilibrium is reached. For realistic couplings we determine the ordering between the separate hydrodynamization, chemical equilibration and thermalization time scales to be $\tau_\text{hydro}Kurkela, AleksiMazeliauskas, AleksasFri, 30 Nov 2018 03:16:06 GMT2018-11-07arXiv:1811.03068http://cds.cern.ch/record/2649391['arXiv:1811.03068']arXiv:1811.03068Chemical equilibration in hadronic collisions
http://cds.cern.ch/record/2649390
We study chemical equilibration in out-of-equilibrium Quark-Gluon Plasma using the first principle method of QCD effective kinetic theory, accurate at weak coupling. In longitudinally expanding systems---relevant for relativistic nuclear collisions---we find that for realistic couplings chemical equilibration takes place after hydrodynamization, but well before local thermalization. We estimate that hadronic collisions with final state multiplicities ${dN_\text{ch}}/{d\eta}\gtrsim 10^2$ live long enough to reach approximate chemical equilibrium, which is consistent with the saturation of strangeness enhancement observed in proton-proton, proton-nucleus and nucleus-nucleus collisions.Kurkela, AleksiMazeliauskas, AleksasFri, 30 Nov 2018 03:16:05 GMT2018-11-07arXiv:1811.03040http://cds.cern.ch/record/2649390['arXiv:1811.03040']arXiv:1811.03040