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H. Fujii

Publications and source records attributed to H. Fujii.

At least 55 records · Page 3Linked to original sources
arXiv2007

Thermal Dileptons at LHC

We predict dilepton invariant-mass spectra for central 5.5 ATeV Pb-Pb collisions at LHC. Hadronic emission in the low-mass region is calculated using in-medium spectral functions of light vector mesons within hadronic many-body theory. In the intermediate-mass region thermal radiation from the Quark-Gluon Plasma, evaluated perturbatively with hard-thermal loop corrections, takes over. An important source over the entire mass range are decays of correlated open-charm hadrons, rendering the nuclear modification of charm and bottom spectra a critical ingredient.

hep-ph↗
arXiv2007

Heavy flavor production in pA collisions

Heavy quark production in high-energy proton-nucleus (pA) collisions is described in the framework of the Color Glass Condensate. kT factorization is broken even at leading order albeit a more general factorization in pA holds at this order in terms of 2, 3 and 4 point correlators of Wilson lines in the nuclear target. The x-evolution of these correlators is computed in the large A and large N mean field limit of the Balitsky-Kovchegov equation. We show results for heavy quark production at RHIC and LHC energies.

hep-ph↗
arXiv2007

Landau Potential Study of the Chiral Phase Transition in a QCD-Like Theory

We investigate the chiral phase transition of a QCD-like theory, based the shape change of the effective potential near the critical point. The potential is constructed with the auxiliary field method, and a source term coupled to the field is introduced in order to compute the potential shape numerically. We also generalize the potential so as to have two independent order parameters, the quark scalar density and the number density. We find a tri-critical point locating at (T,mu)=(97, 203) MeV, and visualize it as the merging point of three potential minima.

hep-ph↗
arXiv2006

Alternativity and reciprocity in the Cayley-Dickson algebra

We calculate the eigenvalue ρof the multiplication mapping R on the Cayley-Dickson algebra A_n. If the element in A_n is composed of a pair of alternative elements in A_{n-1}, half the eigenvectors of R in A_n are still eigenvectors in the subspace which is isomorphic to A_{n-1}. The invariant under the reciprocal transformation A_n \times A_{n} \ni (x,y) -> (-y,x) plays a fundamental role in simplifying the functional form of ρ. If some physical field can be identified with the eigenspace of R, with an injective map from the field to a scalar quantity (such as a mass) m, then there is a one-to-one map π: m \mapsto ρ. As an example, the electro-weak gauge field can be regarded as the eigenspace of R, where πimplies that the W-boson mass is less than the Z-boson mass, as in the standard model.

hep-th↗
arXiv2005

Effective Potential Study of the Chiral Phase Transition in a QCD-like Theory

We construct the effective potential for a QCD-like theory using the auxiliary field method. The chiral phase transition exhibited by the model at finite temperature and the quark chemical potential is studied from the viewpoint of the shape change of the potential near the critical point. We further generalize the effective potential so as to have quark number and scalar quark densities as independent variables near the tri-critical point.

hep-ph↗
arXiv2005

Quark production in high energy proton-nucleus collisions

In this note, we discuss the problem of quark-antiquark pair production in the framework of the color glass condensate. The cross-section can be calculated in closed form for the case of proton-nucleus collisions, where the proton can be considered to be a dilute object. We find that kt-factorization is broken by rescattering effects.

hep-ph↗
arXiv2004

Sigma and hydrodynamic modes along the critical line

Assuming a tricritical point of the two--flavor QCD in the space of temperature, baryon number chemical potential and quark mass, we study the change of the associated soft mode along the critical line within the Ginzburg--Landau approach and the Nambu--Jona-Lasinio model. The ordering density along the chiral critical line is the scalar density whereas a linear combination of the scalar, baryon number and energy densities becomes the proper ordering density along the critical line with finite quark masses. It is shown that the critical eigenmode shifts from the sigma--like fluctuation of the scalar density to a hydrodynamic mode at the tricritical point, where we have two ordering densities, the scalar density and a linear combination of the baryon number and energy densities. We argue that appearance of the critical eigenmode with hydrodynamic character is a logical consequence of divergent susceptibilities of the conserved densities.

hep-ph↗
arXiv2004

Mode Softening near the critical point within effective approaches to QCD

We study the soft mode along the critical line in the phase diagram with the tricritical point, using the Nambu--Jona-Lasinio model. At the critical point with finite quark mass, the ordering density becomes a linear combination of the scalar, quark number and energy densities, and their susceptibilities diverge with the same exponent. Based on the conservation law, it is argued that the divergent susuceptibility of a conserved density must be accompanied by a critically--slowing hydrodynamic mode. The shift of the soft mode from the sigma meson to the hydrodynamic mode occurs at the tricritical point on the critical line.

hep-ph↗
arXiv2004

Soft Modes at the Critical End Point in the Chiral Effective Models

At the critical end point in QCD phase diagram, the scalar, vector and entropy susceptibilities are known to diverge. The dynamic origin of this divergence is identified within the chiral effective models as softening of a hydrodynamic mode of the particle-hole--type motion, which is a consequence of the conservation law of the baryon number and the energy.

hep-ph↗
arXiv2003

Development of a pipeline CAMAC controller with PC/104-Plus single board computer

A pipeline CAMAC controller with PC/104-Plus single board computer has been developed. The architecture of the pipeline CAMAC controller is completely different from that of traditional CAMAC controller. The pipeline CAMAC controller adopted truly pipelined command and data paths from/to computer memory to/from CAMAC. The pipeline method enabled the controller maximum speed of CAMAC, approximately up to 3 MB/sec with 24-bit data. The controller also has a DAQ function such as event numbering for co-existence with other equipment such as VME. Not only the functionality and the performance but also the pipeline architecture and the design concept are described.

physics.ins-det↗
arXiv2003

Pressure induced Superconductor-Insulator transition in the spinel compound CuRh2S4

We performed resistivity measurements in CuRh$_{2}$S$_{4}$ under quasi-hydrostatic pressure of up to 8.0 GPa, and found a pressure induced superconductor-insulator (SI) transition. Initially, with increasing pressure, the superconducting transition temperature $T_c$ increases from 4.7 K at ambient pressure to 6.4 K at 4.0 GPa, but decreases at higher pressures. With further compression, superconductivity in CuRh$_{2}$S$_{4}$ disappears abruptly at a critical pressure $P_{\rm SI}$ between 5.0 and 5.6 GPa, when it becomes an insulator.

cond-mat.supr-con↗
arXiv2003

The Data Acquisition System Based on PMC Bus

High energy physics experiments in KEK/Japan rush into over KHz trigger stage. Thus, we need a successor of the data acquisition(DAQ) system that replaces the CAMAC or FASTBUS systems. To meet these needs, we have developed a DAQ system which includes a crate, base-board modules, daughter cards for front-end A/D or T/D conversion, and back-end communication cards for data transfer and timing control. The size of the crate is for the 9U Euro-cards with the standard VME32 bus and extension connectors for power supply. The base-board comprises of a local bus with the sequencer connected to the front-end daughter cards via event buffering FIFOs, and the standard PMC (PCI mezzanine card) bus to be set a PMC processor unit to reduce data size from the front-end daughter cards. A data transfer module, which is connected to the event building system, and a trigger control unit, which communicates with the central timing controller are installed on the back-end communication card connected to the rear end of the base-board. We describe the design of this DAQ system and evaluate the performance of it.

physics.ins-det↗
arXiv2003

Development of a PCI Based Data Acquisition Platform for High Intensity Accelerator Experiments

Data logging at an upgraded KEKB accelerator or the J-PARC facility, currently under commission, requires a high density data acquisition platform with integrated data reduction CPUs. To follow market trends, we have developed a DAQ platform based on the PCI bus, a choice which permits a fast DAQ and a long expected lifetime of the system. The platform is a 9U-VME motherboard consisting of four slots for signal digitization modules, readout FIFOs for data buffering, and three PMC slots, on one of which resides a data reduction CPU. We have performed long term and thermal stability tests. The readout speed on the platform has been measured up to 125 MB/s in DMA mode.

hep-ex↗
arXiv2003

Scalar density fluctuation at critical end point in NJL model

Soft mode near the critical end point in the phase diagram of two-flavor Nambu--Jona-Lasinio (NJL) model is investigated within the leading 1/N_c approximation with N_c being the number of the colors. It is explicitly shown by studying the spectral function of the scalar channel that the relevant soft mode is the scalar density fluctuation, which is coupled with the quark number density, while the sigma meson mode stays massive.

hep-ph↗
arXiv2002

J/psi suppression in heavy ion collisions by quark momentum diffusion

The momentum diffusion effect of the quark pair due to the multiple scattering in a nuclear medium is studied to explain the observed J/psi yields in SPS experiments. The resulting suppression is found to be insufficient to reproduce the J/psi yield in Pb-Pb collisions at SPS energy.

hep-ph↗
arXiv2002

Superpenetration of a high energy Q barQ bound state through random color fields

The transmission amplitude of a color dipole through a random external color field is computed in the eikonal approximation in order to study the absorption of high energy quarkonium by nuclear target. It is shown that the internal color state of the dipole becomes randomized and all possible color states are eventually equi-partitioned, while the probability of finding a color singlet bound state attenuates not exponentially, but inversely proportional to the distance L of the random field zone which the dipole has traveled.

nucl-th↗