Searcharxiv⌕ Search

arXiv subjects

F. M. Liu

Publications and source records attributed to F. M. Liu.

At least 19 recordsLinked to original sources
arXiv2014

Reconfigurable on-chip entangled sources based on lithium-niobate waveguide circuits

Integrated quantum optics becomes a consequent tendency towards practical quantum information processing. Here, we report the on-chip generation and manipulation of photonic entanglement based on reconfigurable lithium niobate waveguide circuits. By introducing periodically poled structure into the waveguide interferometer, two individual photon-pair sources with controllable phase-shift are produced and cascaded by a quantum interference, resulting in a deterministically separated identical photon pair. The state is characterized by 92.9% visibility Hong-Ou-Mandel interference. Continuous morphing from two-photon separated state to bunched state is further demonstrated by on-chip control of electro-optic phase-shift. The photon flux reaches ~1.4*10^7 pairs nm-1 mW-1. Our work presents a scenario for on-chip engineering of different photon sources and paves a way to the fully integrated quantum technologies.

quant-ph↗
arXiv2004

Chemical equilibration due to heavy Hagedorn states

A scenario of heavy resonances, called massive Hagedorn states, is proposed which exhibits a fast ($t\approx 1$ fm/c) chemical equilibration of (strange) baryons and anti-baryons at the QCD critical temperature $T_c$. For relativistic heavy ion collisions this scenario predicts that hadronization is followed by a brief expansion phase during which the equilibration rate is higher than the expansion rate, so that baryons and antibaryons reach chemical equilibrium before chemical freeze-out occurs.

hep-ph↗
arXiv2004

Production of Theta(1540) and Xi Pentaquark States in Proton-Proton Interactions

The production of strange pentaquark states (e.g. Theta baryons and Xi^-- states) in hadronic interactions within a Gribov-Regge approach is explored. In this approach the Theta^+(1540) and the Xi Pentaquark are produced by disintegration of remnants formed by the exchange of pomerons between the two protons. We predict the rapidity and transverse momentum distributions as well as the 4 pi multiplicity of the Theta^+, Xi^--, Xi^-, Xi^0 and Xi^+ for sqrt{s} = 17 GeV (SPS) and 200 GeV (RHIC). For both energies more than 10^{-3} Theta^+ and more than 10^{-5} Xi per pp event should be observed by the present experiments.

hep-ph↗
arXiv2003

Micro-Canonical Hadron Production in pp collisions

We apply a microcanonical statistical model to investigate hadron production in pp collisions. The parameters of the model are the energy E and the volume V of the system, which we determine via fitting the average multiplicity of charged pions, protons and antiprotons in pp collisions at different collision energies. We then make predictions of mean multiplicities and mean transverse momenta of all identified hadrons. Our predictions on nonstrange hadrons are in good agreement with the data, the mean transverse momenta of strange hadron as well. However, the mean multiplicities of strange hadrons are overpredicted. This agrees with canonical and grandcanonical studies, where a strange suppression factor is needed. We also investigate the influence of event-by-event fluctuations of the E parameter.

hep-ph↗
arXiv2003

Hadron Production in Proton-Proton Scattering in NEXUS3

Using the recently introduced model NEXUS 3, we calculate for proton-proton, neutron-proton and antiproton-proton collisions the excitation function of particle yields and of average transverse momenta of different particle species as well as rapidity, x_{F} and transverse momentum distributions. Our results are compared with available data in between sqrt{s} = 5 GeV and 65 GeV. We find for all observables quite nice agreement with data what make this model to a useful tool to study particle production in elementary hadronic reactions.

hep-ph↗
arXiv2003

A Micro-Canonical Description of Hadron Production in Proton-Proton Collisions

A micro-canonical treatment is used to study particle production in pp collisions. First this micro-canonical treatment is compared to some canonical ones. Then proton, antiproton and pion 4(π) multiplicities from proton-proton collisions at various center of mass energies are used to fix the micro-canonical parameters (E) and (V). The dependences of the micro-canonical parameters on the collision energy are parameterised for the further study of pp reactions with this micro-canonical treatment.

hep-ph↗
arXiv2003

High PT Suppression without Jet Quenching in Au+Au Collisions in NEXUS

Problem of high PT suppression in RHIC data is generally associated to jet quenching in a dense medium. We recently proposed a new approach to high energy nuclear scattering, which treats the initial stage of heavy ion collisions in a sophisticated way, and whose numerical solution is the model NEXUS. Within this model, there is no jet quenching, but the explicit energy conservation leads to similar results. RHIC high PT ratio between AA and pp results can be reproduced for different centrality bins.

hep-ph↗
arXiv2003

Strange Particles from NEXUS 3

After discussing conceptual problems with the conventional string model, we present a new approach, based on a theoretically consistent multiple scattering formalism. First results for strange particle production in proton-proton scattering at 158 GeV and at 200 GeV (cms) are discussed.

hep-ph↗
arXiv2003

A New String Model: NEXUS 3

After discussing conceptual problems with the conventional string model, we present a new approach, based on a theoretically consistent multiple scattering formalism. First results for proton-proton scattering at 158 GeV are discussed.

hep-ph↗
arXiv2003

Comparison of Microcanonical and Canonical Hadronization

Average multiplicities and transverse momenta of hadrons are calculated using a microcanonical hadronization description for a cluster of given total energy and volume. As a function of the total energy, we determine the critical volume above which the microcanonical description coincides with the canonical one, and compare the results with those obtained using one of standard canonical models. We show that the critical volume depends on the energy and the mass of the hadrons. For heavy particles, volumes above $50 fm^{3}$ are needed, even more than$100 fm^{3}$ if one considers transverse momenta. Thus the prediction of heavy hadron multiplicities in pp, Kp, and $e^{+}e^{-}$ reactions requires a microcanonical approach, whereas for heavy ion reactions a canonical calculation is valid. We conclude by showing the importance of the feeding for the observed hadron multiplicities.

hep-ph↗
arXiv2002

A Novel Mechanism of H^0 Di-baryon Production in Proton-Proton Interactions from Parton Based Gribov-Regge Theory

A novel mechanism of H^0 and strangelet production in hadronic interactions within the Gribov-Regge approach is presented. In contrast to traditional distillation approaches, here the production of multiple (strange) quark bags does not require large baryon densities or a QGP. The production cross section increases with center of mass energy. Rapidity and transverse momentum distributions of the H^0 are predicted for pp collisions at E_lab = 160 AGeV (SPS) and \sqrt s = 200 AGeV (RHIC). The predicted total H^0 multiplicities are of order of the Omega-baryon yield and can be accessed by the NA49 and the STAR experiments.

hep-ph↗
arXiv2002

Probing Hadronization with Strangeness

The Omega-bar/Omega ratio originating from string decays is predicted to be larger than unity in proton-proton interaction at SPS energies. The anti-omega dominance increases with decreasing beam energy. This surprising behavior is caused by the combinatorics of quark-antiquark production in small and low-mass strings. Since this behavior is not found in a statistical description of hadron production in proton-proton collisions, it may serve as a key observable to probe the hadronization mechanism in such collisions.

nucl-th↗
arXiv2002

Initial Condition for QGP Evolution from NEXUS

We recently proposed a new approach to high energy nuclear scattering, which treats the initial stage of heavy ion collisions in a sophisticated way. We are able to calculate macroscopic quantities like energy density and velocity flow at the end of this initial stage, after the two nuclei having penetrated each other. In other words, we provide the initial conditions for a macroscopic treatment of the second stage of the collision. We address in particular the question of how to incorporate the soft component properly. We find almost perfect "Bjorken scaling": the rapidity coincides with the space-time rapidity, whereas the transverse flow is practically zero. The distribution of the energy density in the transverse plane shows typically a very "bumpy" structure.

hep-ph↗
arXiv2001

Overpopulation of $\bar Ω$ in pp collisions: a way to distinguish statistical hadronization from string dynamics

The $\barΩ/Ω$ ratio originating from string decays is predicted to be larger than unity in proton proton interactions at SPS energies ($E_{\rm lab}$=160 GeV). The anti-omega dominance increases with decreasing beam energy. This surprising behavior is caused by the combinatorics of quark-antiquark production in small and low-mass strings. Since this behavior is not found in a statistical description of hadron production in proton proton collisions, it may serve as a key observable to probe the hadronization mechanism in such collisions.

hep-ph↗
arXiv2001

Consistent Treatment of Soft and Hard Processes in Hadronic Interactions

The QCD improved parton model is a very successful concept to treat processes in hadronic interactions, whenever large partonic transverse momenta are involved. However, cross sections diverge in the limit p_T -> 0, and the usual treatment is the definition of a lower cutoff p_T_min, such that processes with a smaller p_T -- so-called soft processes -- are simply ignored, which is certainly not correct for example at RHIC energies. A more consistent procedure amounts to introduce a technical parameter Q_0^2, referred to as soft virtuality scale, which is nothing but an artificial borderline between soft and hard physics. We will discuss such a formalism, which coincides with the improved parton model for high p_T processes and with the phenomenological treatment of soft scattering, when only small virtualities are involved. The most important aspect of our approach is that it allows to obtain a smooth transition between soft and hard scattering, and therefore no artificial dependence on a cutoff parameter should appear.

hep-ph↗