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125

Jul 20, 2013
07/13

by
K. J. Eskola; K. Kajantie; K. Tuominen

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We compute the centrality dependence of multiplicities of particles produced in ultrarelativistic nuclear collisions at various energies and atomic numbers. The computation is carried out in perturbative QCD with saturated densities of produced gluons and by including effects of nuclear geometry. Numbers are given for Au+Au collisions at RHIC energies.

Source: http://arxiv.org/abs/hep-ph/0009246v1

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47

Sep 24, 2013
09/13

by
P. F. Kolb; U. Heinz; P. Huovinen; K. J. Eskola; K. Tuominen

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The centrality dependence of the charged multiplicity, transverse energy, and elliptic flow coefficient is studied in a hydrodynamic model, using a variety of different initializations which model the initial energy or entropy production process as a hard or soft process, respectively. While the charged multiplicity depends strongly on the chosen initialization, the p_t-integrated elliptic flow for charged particles as a function of charged particle multiplicity and the p_t-differential...

Source: http://arxiv.org/abs/hep-ph/0103234v3

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45

Sep 22, 2013
09/13

by
A. Mocsy; F. Sannino; K. Tuominen

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We illustrate why color deconfines when chiral symmetry is restored in gauge theories with quarks in the fundamental representation, and while these transitions do not need to coincide when quarks are in the adjoint representation, entanglement between them is still present.

Source: http://arxiv.org/abs/hep-ph/0403160v1

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43

Sep 22, 2013
09/13

by
A. Mocsy; F. Sannino; K. Tuominen

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The order parameter for the pure Yang-Mills phase transition is the Polyakov loop, which encodes the symmetries of the Z_N center of the SU(N) gauge group. The physical degrees of freedom of any asymptotically free gauge theory are hadronic states. Using the Yang-Mills trace anomaly and the exact Z_N symmetry we show that the transfer of information from the order parameter to hadrons is complete.

Source: http://arxiv.org/abs/hep-ph/0310078v1

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40

Sep 23, 2013
09/13

by
K. Tuominen

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We investigate the interplay between chiral symmetry restoration and deconfinement both in two color QCD and adjoint QCD. In ordinary QCD we show how the behavior of the Polyakov loop near chiral phase transition is induced by the chiral order parameter, while in adjoint two color QCD one has two truly independent phase transitions. Introducing a finite baryochemical potential we find that adjoint QCD exhibits tetracritical behavior.

Source: http://arxiv.org/abs/hep-ph/0408330v1

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41

Sep 23, 2013
09/13

by
T. Kähärä; M. Ruggieri; K. Tuominen

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The interplay of deconfinement and chiral symmetry restoration are considered in terms of effective theories. We generalize the earlier model studies by considering fermions in higher representations, and study the finite temperature phase diagrams of SU(2) and SU(3) gauge theories with two fermion flavors in fundamental, adjoint or two-index symmetric representations. We discuss our results in relation to recent lattice simulations on these theories and outline possible applications in the...

Source: http://arxiv.org/abs/1202.1769v1

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52

Sep 18, 2013
09/13

by
T. Kahara; K. Tuominen

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We study two effective models for QCD, the Nambu-Jona-Lasinio -model and the linear sigma model extended by including a Polyakov loop potential, which is fitted to reproduce pure gauge theory thermodynamics, and a coupling between the chiral fields and the Polyakov loop. Thus the resulting models have as relevant degrees of freedom the Polyakov loop and chiral fields. By comparing the extended models with the bare chiral models we can conclude that the addition of the Polyakov loop is necessary...

Source: http://arxiv.org/abs/0803.2598v1

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49

Sep 19, 2013
09/13

by
K. Tuominen

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Saturation models for particle production in relativistic nuclear collisions are discussed. In particular, I show that the predictions from the high density QCD for the qualitative shape of $dN/dy$ are very sensitive to the form of the unintegrated gluon distribution.

Source: http://arxiv.org/abs/hep-ph/0209102v1

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Sep 22, 2013
09/13

by
T. Kahara; K. Tuominen

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We study effective models of chiral fields and Polyakov loop expected to describe the dynamics responsible for the phase structure of two-flavor QCD. We consider chiral sector described either using linear sigma model or Nambu-Jona-Lasinio model and study how these models, on the mean-field level when coupled with the Polyakov loop, behave as a function of increasing bare quark (or pion) mass. We find qualitatively similar behaviors for the cases of linear sigma model and Nambu-Jona-Lasinio...

Source: http://arxiv.org/abs/0906.0890v1

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Jun 30, 2018
06/18

by
R. Paatelainen; K. J. Eskola; H. Niemi; K. Tuominen

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We review the recent results from the computation of saturated next-to-leading order perturbative QCD minijet intial conditions combined with viscous hydrodynamical evolution of ultrarelativistic heavy-ion collisions at the LHC and RHIC. Comparison with experimental data is shown.

Topic: High Energy Physics - Phenomenology

Source: http://arxiv.org/abs/1406.4760

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55

Sep 22, 2013
09/13

by
K. J. Eskola; K. Kajantie; K. Tuominen

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Atomic number ($A$) and energy ($\roots$) scaling exponents of multiplicity and transverse energy in heavy ion collisions are analytically derived in the perturbative QCD + saturation model. The exponents depend on the small-$x$ behaviour of gluon distribution functions at an $x$-dependent scale. The relation between initial state and final state saturation is also discussed.

Source: http://arxiv.org/abs/hep-ph/0106330v1

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Sep 18, 2013
09/13

by
D. D. Dietrich; F. Sannino; K. Tuominen

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We investigate theories in which the technifermions in higher dimensional representations of the technicolor gauge group dynamically break the electroweak symmetry of the standard model. For the two-index symmetric representation of the gauge group the lowest number of techniflavors needed to render the underlying gauge theory quasi conformal is two. We confront the models with the recent electroweak precision measurements and demonstrate that the two technicolor theory is a valid candidate for...

Source: http://arxiv.org/abs/hep-ph/0505059v1

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66

Jul 20, 2013
07/13

by
K. J. Eskola; K. Tuominen

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Final state average transverse energy and charged particle multiplicity at the central rapidity unit of central Au-Au collisions at RHIC are studied within a framework of lowest order perturbative QCD and Bjorken's hydrodynamical picture. In particular, effects of initial minijet production and the $pdV$ work during the subsequent evolution of the QGP are investigated. Nuclear shadowing effects are included in a consistent manner, and the dependence of the results on the minijet transverse...

Source: http://arxiv.org/abs/hep-ph/9906438v1

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77

Jul 20, 2013
07/13

by
J. Alanen; T. Alho; K. Kajantie; K. Tuominen

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We use gauge/gravity duality to study simultaneously the mass spectrum and the thermodynamics of a generic quasi-conformal gauge theory, specified by its beta function. The beta function of a quasi-conformal theory almost vanishes, and the coupling is almost constant between two widely separated energy scales. Depending on whether the gravity dual has a black hole or not, the mass spectrum is either a spectrum of quasinormal oscillations or a normal T=0 mass spectrum. The mass spectrum is...

Source: http://arxiv.org/abs/1107.3362v1

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51

Sep 22, 2013
09/13

by
M. Antola; S. Di Chiara; F. Sannino; K. Tuominen

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We introduce novel extensions of the Standard Model featuring a supersymmetric technicolor sector. First we consider N=4 Super Yang-Mills which breaks to N=1 via the electroweak (EW) interactions and coupling to the MSSM. This is a well defined, economical and calculable extension of the SM involving the smallest number of fields. It constitutes an explicit example of a natural supersymmetric conformal extension of the Standard Model featuring a well defined connection to string theory. It...

Source: http://arxiv.org/abs/1001.2040v3

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57

Sep 18, 2013
09/13

by
R. Paatelainen; K. J. Eskola; H. Holopainen; K. Tuominen

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We bring the EKRT framework, which combines perturbative QCD (pQCD) minijet production with gluon saturation and hydrodynamics, to next-to-leading order (NLO) in pQCD as rigorously as possible. We chart the model uncertainties, and study the viability and predictive power of the model in the light of the RHIC and LHC measurements in central $A+A$ collisions. In particular, we introduce a new set of measurement functions to define the infrared- and collinear-safe minijet transverse energy,...

Source: http://arxiv.org/abs/1211.0461v1

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49

Sep 21, 2013
09/13

by
K. J. Eskola; P. V. Ruuskanen; S. S. Rasanen; K. Tuominen

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We compute the particle multiplicities and transverse energies at central and nearly central AA collisions at RHIC and LHC. The initial state is computed from perturbative QCD supplemented by the conjecture of saturation of produced partons. The expansion stage is described in terms of hydrodynamics assuming longitudinal boost invariance and azimuthal symmetry. Transverse flow effects, a realistic list of hadrons and resonance decays are included. Comparison with the data of the multiplicities...

Source: http://arxiv.org/abs/hep-ph/0104010v2

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7.0

Jun 30, 2018
06/18

by
R. Paatelainen; K. J. Eskola; H. Holopainen; H. Niemi; K. Tuominen

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We calculate initial conditions for the hydrodynamical evolution in ultrarelativistic heavy-ion collisions at the LHC and RHIC in an improved next-to-leading order perturbative QCD + saturation framework. Using viscous relativistic hydrodynamics, we show that we obtain a good simultaneous description of the centrality dependence of charged particle multiplicities, transverse momentum spectra and elliptic flow at the LHC and at RHIC. In particular, we discuss how the temperature dependence of...

Topic: High Energy Physics - Phenomenology

Source: http://arxiv.org/abs/1401.5319

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45

Sep 22, 2013
09/13

by
T. Alho; M. Jarvinen; K. Kajantie; E. Kiritsis; K. Tuominen

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Holographic models in the T=0 universality class of QCD in the limit of large number N_c of colors and N_f massless fermion flavors, but constant ratio x_f=N_f/N_c, are analyzed at finite temperature. The models contain a 5-dimensional metric and two scalars, a dilaton sourcing TrF^2 and a tachyon dual to \bar qq. The phase structure on the T,x_f plane is computed and various 1st order, 2nd order transitions and crossovers with their chiral symmetry properties are identified. For each x_f, the...

Source: http://arxiv.org/abs/1210.4516v1

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6.0

Jun 30, 2018
06/18

by
LAGUNA-LBNO Collaboration; :; S. K. Agarwalla; L. Agostino; M. Aittola; A. Alekou; B. Andrieu; F. Antoniou; R. Asfandiyarov; D. Autiero; O. Bésida; K. Nikolics; E. Noah; Yu. Novikov; A. Oprima; J. Osborne; T. Ovsyannikova; Y. Papaphilippou; S. Pascoli; T. Patzak; M. Pectu; A. Balik; E. Pennacchio; L. Periale; H. Pessard; B. Popov; M. Ravonel; M. Rayner; F. Resnati; O. Ristea; A. Robert; A. Rubbia; P. Ballett; K. Rummukainen; A. Saftoiu; K. Sakashita; F. Sanchez-Galan; J. Sarkamo; N. Saviano;...

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One of the main goals of the Long Baseline Neutrino Observatory (LBNO) is to study the $L/E$ behaviour (spectral information) of the electron neutrino and antineutrino appearance probabilities, in order to determine the unknown CP-violation phase $\delta_{CP}$ and discover CP-violation in the leptonic sector. The result is based on the measurement of the appearance probabilities in a broad range of energies, covering t he 1st and 2nd oscillation maxima, at a very long baseline of 2300 km. The...

Topics: High Energy Physics - Phenomenology, High Energy Physics - Experiment

Source: http://arxiv.org/abs/1412.0593

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43

Sep 18, 2013
09/13

by
T. Karavirta; K. Rummukainen; K. Tuominen

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Lattice simulations on SU(2) and SU(3) gauge theories with matter fields in the fundamental, adjoint and two index symmetric representations are needed to determine if these theories are near or within the conformal window as required for their applications in beyond standard model phenomenology. Simulations with Wilson fermion action are subject to artifacts linear in the lattice spacing $a$, and must be improved. We provide the necessary coefficients for perturbative improvement of the...

Source: http://arxiv.org/abs/1201.1883v1

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7.0

Jun 28, 2018
06/18

by
H. Niemi; K. J. Eskola; R. Paatelainen; K. Tuominen

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We compute the initial energy densities produced in ultrarelativistic heavy-ion collisions from NLO perturbative QCD using a saturation conjecture to control soft particle production, and describe the subsequent space-time evolution of the system with hydrodynamics, event by event. The resulting centrality dependence of the low-$p_T$ observables from this pQCD + saturation + hydro ("EKRT") framework are then compared simultaneously to the LHC and RHIC measurements. With such an...

Topics: Nuclear Theory, High Energy Physics - Phenomenology

Source: http://arxiv.org/abs/1512.05132

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6.0

Jun 28, 2018
06/18

by
H. Niemi; K. J. Eskola; R. Paatelainen; K. Tuominen

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We compute predictions for various low-transverse-momentum bulk observables in $\sqrt{s_{NN}} = 5.023$ TeV Pb+Pb collisions at the LHC from the event-by-event next-to-leading-order perturbative-QCD + saturation + viscous hydrodynamics ("EKRT") model. In particular, we consider the centrality dependence of charged hadron multiplicity, flow coefficients of the azimuth-angle asymmetries and correlations of event-plane angles. The centrality dependencies of the studied observables are...

Topics: Nuclear Theory, High Energy Physics - Phenomenology

Source: http://arxiv.org/abs/1511.04296

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41

Sep 18, 2013
09/13

by
K. J. Eskola; K. Tuominen

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We compute in next-to-leading order (NLO) perturbative QCD the transverse energy carried into the central rapidity unit of hadron or nuclear collisions by the partons freed in the few-GeV subcollisions. The formulation is based on a rapidity window and a measurement function of a new type. The behaviour of the NLO results as a function of the minimum transverse momentum and as a function of the scale choice is studied. The NLO results are found to be stable relative to the leading-order ones...

Source: http://arxiv.org/abs/hep-ph/0002008v2

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13

Jun 26, 2018
06/18

by
T. Alho; M. Jarvinen; K. Kajantie; E. Kiritsis; K. Tuominen

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We consider the finite temperature phase diagram of holographic QCD in the Veneziano limit (Nc large, Nf large with xf=Nf/Nc fixed) and calculate one string-loop corrections to the free energy in certain approximations. Such corrections, especially due to the pion modes are unsuppressed in the Veneziano limit. We find that under some extra assumptions the first order transition following from classical gravity solutions can become second order. If stringy asymptotics are of a special form and...

Topics: High Energy Physics - Phenomenology, High Energy Physics - Lattice, Nuclear Theory, High Energy...

Source: http://arxiv.org/abs/1501.06379

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64

Sep 20, 2013
09/13

by
K. J. Eskola; K. Kajantie; P. V. Ruuskanen; K. Tuominen

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We compute the rapidity dependence of particle and transverse energy production in ultrarelativistic heavy ion collisions at various beam energies and atomic numbers using the perturbative QCD + saturation model. The distribution is a broad gaussian near $y=0$ but the rapid increase of particle production with the beam energy will via energy conservation strongly constrain the rapidity distribution at large $y$.

Source: http://arxiv.org/abs/hep-ph/0204034v1

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43

Sep 18, 2013
09/13

by
K. Tuominen

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This talk will discuss how to compute initial quantites in heavy ion collisions at RHIC (200 AGeV) and at LHC (5500 AGeV) using perturbative QCD (pQCD) by including the next-to-leading order (NLO) corrections and a dynamical determination of the dominant physical scale. The initial numbers are converted into final ones by assuming kinetic thermalization and adiabatic expansion.

Source: http://arxiv.org/abs/hep-ph/0008149v1

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72

Sep 19, 2013
09/13

by
J. T. Lenaghan; K. Tuominen

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We study the effects of gluon saturation on pion production in high energy proton-nucleus collisions using the color glass condensate model. At high p_perp, we show that the p_perp-distribution of gluons behaves as ~ 1/(p_perp^7) in accordance with both conventional perturbative QCD calculations and experiment. Fragmentation of gluons into pions leads to a rapidity dependent depletion of pions relative to the conventional perturbative QCD predictions. We argue that these clear and systematic...

Source: http://arxiv.org/abs/hep-ph/0208007v1

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54

Sep 23, 2013
09/13

by
K. J. Eskola; K. Kajantie; P. V. Ruuskanen; K. Tuominen

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We compute how the initial energy density and produced gluon, quark and antiquark numbers scale with atomic number and beam energy in ultrarelativistic heavy ion collisions. The computation is based on the argument that the effect of all momentum scales can be estimated by performing the computation at one transverse momentum scale, the saturation momentum. The initial numbers are converted to final ones by assuming kinetic thermalisation and adiabatic expansion. The main emphasis of the study...

Source: http://arxiv.org/abs/hep-ph/9909456v1

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59

Sep 18, 2013
09/13

by
P. Hoyer; J. T. Lenaghan; K. Tuominen; C. Vogt

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The interaction region of hard exclusive hadron scattering can have a large transverse size due to endpoint contributions, where one parton carries most of the hadron momentum. The endpoint region is enhanced and can dominate in processes involving multiple scattering and quark helicity flip. The endpoint Fock states have perturbatively short lifetimes and scatter softly in the target. We give plausible arguments that endpoint contributions can explain the apparent absence of color transparency...

Source: http://arxiv.org/abs/hep-ph/0210124v2

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11

Jun 30, 2018
06/18

by
LAGUNA-LBNO Collaboration; :; S. K. Agarwalla; L. Agostino; M. Aittola; A. Alekou; B. Andrieu; F. Antoniou; R. Asfandiyarov; D. Autiero; O. Bésida; K. Nikolics; E. Noah; Yu. Novikov; A. Oprima; J. Osborne; T. Ovsyannikova; Y. Papaphilippou; S. Pascoli; T. Patzak; M. Pectu; A. Balik; E. Pennacchio; L. Periale; H. Pessard; B. Popov; M. Ravonel; M. Rayner; F. Resnati; O. Ristea; A. Robert; A. Rubbia; P. Ballett; K. Rummukainen; A. Saftoiu; K. Sakashita; F. Sanchez-Galan; J. Sarkamo; N. Saviano;...

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The proposed Long Baseline Neutrino Observatory (LBNO) initially consists of $\sim 20$ kton liquid double phase TPC complemented by a magnetised iron calorimeter, to be installed at the Pyh\"asalmi mine, at a distance of 2300 km from CERN. The conventional neutrino beam is produced by 400 GeV protons accelerated at the SPS accelerator delivering 700 kW of power. The long baseline provides a unique opportunity to study neutrino flavour oscillations over their 1st and 2nd oscillation maxima...

Topics: High Energy Physics - Phenomenology, High Energy Physics - Experiment

Source: http://arxiv.org/abs/1412.0804

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46

Sep 17, 2013
09/13

by
J. Alanen; K. Kajantie; K. Tuominen

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We use gauge/gravity duality to study the thermodynamics of a generic almost conformal theory, specified by its beta function. Three different phases are identified, a high temperature phase of massless partons, an intermediate quasi-conformal phase and a low temperature confining phase. The limit of a theory with infrared fixed point, in which the coupling does not run to infinity, is also studied. The transitions between the phases are of first order or continuous, depending on the parameters...

Source: http://arxiv.org/abs/1003.5499v1

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64

Sep 19, 2013
09/13

by
K. J. Eskola; K. Tuominen

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We compute in next-to-leading order (NLO) perturbative QCD the amount of transverse energy produced into a rapidity region $\Delta Y$ of a nuclear collision from partons created in the few-GeV subcollisions. The NLO formulation assumes collinear factorization and is based on the subtraction method. We first study the results as a function of the minimum transverse momentum scale and define and determine the associated $K$-factors. The dependence of the NLO results on the scale choice and on the...

Source: http://arxiv.org/abs/hep-ph/0010319v1

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62

Sep 19, 2013
09/13

by
M. Antola; M. Heikinheimo; F. Sannino; K. Tuominen

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We explore the scenario in which the breaking of the electroweak symmetry is due to the simultaneous presence and interplay of a dynamical sector and an unnatural elementary Higgs. We introduce a low energy effective Lagrangian and constrain the various couplings via direct search limits and electroweak and flavor precision tests. We find that the model we study is a viable model of dynamical breaking of the electroweak symmetry.

Source: http://arxiv.org/abs/0910.3681v1