arXiv subjects

D. E. Kahana

Publications and source records attributed to D. E. Kahana.

At least 19 recordsLinked to original sources

arXiv2015

LHCb $P_c^+$ Resonances as Molecular States

Recent experiments at the LHCb detector have once again raised the possibility that quark bags may exist containing more than three quarks. Specifically the LHCb collaboration points to evidence for hadronic resonances decaying into J/$ψ$ and proton: the $P_c(4450)^+$ and $P_C(4380)^+$. Here we put forth a case that a reasonable description of these states is possible as molecular resonances of a $p$ and a J/$ψ$. Our model seems to accommodate the observed states and their measured widths, both the lower lying, broader, negative parity state and the higher lying, narrow positive parity state. If these resonances do indeed exist one might envision a rich spectroscopy of such pentaquark states waiting to be discovered, though this would deepen the mystery of their absence in earlier hadron spectroscopy. Perhaps the presence of the heavy charmed quarks, as well as the lighter u,d and s quarks, is the determining factor.

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arXiv2011

Higgs and Top Masses from Dynamical Symmetry Breaking - Revisited

We re-examine our former predictions \cite{kahanath1,kahanath2} of the top and Higgs masses via dynamical symmetry breaking in a 4-fermion theory which produces the Higgs as a bound state, and relates the top and Higgs masses to $m_W$. The use of dynamical symmetry breaking was stongly motivated by the apparent equality, within a factor of two, of the known and expected masses of the $W$, $Z$, top and Higgs. In later work \cite{kahanath2} we evaluated the masses self-consistently at the mass-poles, which resulted in predictions of $m_t \sim 175$ GeV, and $m_H \sim 125$ GeV as central values within ranges produced by varying the measured strong coupling. Figures (1) and (2) result from evolution down to $m_W$ while the number quoted for the top quark mass, i.e. 175 GeV includes an evolution back up to the top and use of the determination of $α_s$ at LEP at that time. $m_H$ is less dependent on the value of the strong coupling. The variation of the predicted masses for a range of the strong and electro-weak couplings $α_s$, $α_W$ at $m_W$ are exhibited in Figure (3) and Figure (4) reproduced from the last work \cite{kahanath2}, which was submitted to PRD well before the first FNAL publications \cite{CDF1,D0top} suggesting evidence for the top.

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arXiv2010

J/Psi Production by Charm Quark Coalescence

Production of $c\bar c$ pairs in elementary hadron-hadron collisions is introduced in a simulation of relativistic heavy ion collisions. Coalescence of charmed quarks and antiquarks into various charmonium states is performed and the results are compared to PHENIX J$/ψ$ Au+Au data. The $χ$ and $ψ$' bound states must be included as well as the ground state J$/ψ$, given the appreciable feeding from the excited states down to the J$/ψ$ via gamma decays. Charmonium coalescence is found to take place at relatively late times: generally after $c$($\bar c$)-medium interactions have ceased. Direct production of charmonia through hadron-hadron interactions, {\it ie.} without explicit presence of charm quarks, occurring only at early times, is suppressed by collisions with comoving particles and accounts for some $\sim 5\%$ of the total J$/ψ$ production. Coalescence is especially sensitive to the level of open charm production, scaling naively as $n_{c\bar c}^2$. The J$/ψ$ transverse momentum distribution is dependent on the charm quark transverse momentum distribution and early charm quark-medium interaction, thus providing a glimpse of the initial collision history.

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arXiv2007

Elliptical Flow in Relativistic Ion Collisions at s^(1/2)= 200 A GeV

A consistent picture of the Au+Au and D+Au, s^1/2 = 200 A GeV measurements at RHIC obtained with the PHENIX, STAR, PHOBOS and BRAHMS detectors including both the rapidity and transverse momentum spectra was previously developed with the simulation LUCIFER. The approach was modeled on the early production of a fluid of pre-hadrons after the completion of an initial, phase of high energy interactions. The formation of pre-hadrons is discussed here, in a perturbative QCD approach as advocated by Kopeliovich, Nemchik and Schmidt. In the second phase of LUCIFER, a considerably lower energy hadron-like cascade ensues. Since the dominant collisions occurring in this latter phase are meson-meson in character while the initial collisions are between baryons, i.e. both involve hadron sized interaction cross-sections, there is good reason to suspect that the observed elliptical flow will be produced naturally, and this is indeed found to be the case.

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arXiv2007

Suppression of High Transverse Momentum $π^0$ Spectra in Au+Au Collisions at RHIC

Au+Au, $s^{1/2} = 200$ A GeV measurements at RHIC, obtained with the PHENIX, STAR, PHOBOS and BRAHMS detectors, have all indicated a suppression of neutral pion production, relative to an appropriately normalized NN level. For central collisions and vanishing pseudo-rapidity these experiments exhibit suppression in charged meson production, especially at medium to large transverse momenta. In the PHENIX experiment similar behavior has been reported for $π^0$ spectra. In a recent work on the simpler D+Au interaction, to be considered perhaps as a tune-up for Au+Au, we reported on a pre-hadronic cascade mechanism which explains the mixed observation of moderately reduced $p_\perp$ suppression at higher pseudo-rapidity as well as the Cronin enhancement at mid-rapidity. Here we present the extension of this work to the more massive ion-ion collisions. Our major thesis is that much of the suppression is generated in a late stage cascade of colourless pre-hadrons produced after an initial short-lived coloured phase. We present a pQCD argument to justify this approach and to estimate the time duration $τ_p$ of this initial phase. Of essential importance is the brevity in time of the coloured phase existence relative to that of the strongly interacting pre-hadron phase. The split into two phases is of course not sharp in time, but adequate for treating the suppression of moderate and high $p_\perp$ mesons.

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arXiv2005

Au+Au Collisions: the Suppression of High Transverse Momentum in Neutral pion Spectra

Au+Au, $\sqrt{s} = 200$ A GeV measurements at RHIC, obtained with the PHENIX, STAR, PHOBOS and BRAHMS detectors, have all indicated a suppression of production, relative to an appropriately normalized NN level. For central collisions and vanishing pseudo-rapidity these experiments indicate a considerable reduction, relative to that nominally expected from equivalent PP measurements, in charged and particle production, especially at mid- to large transverse momenta. In the PHENIX experiment similar behavior has been reported for $π^0$ spectra. In a recent work \cite{luc4brahms} on the presumably simpler D+Au interaction, to be considered perhaps as a tune-up for Au+Au, we reported on a hadronic cascade mechanism which can explain the observed moderatereduced $p_\perp$ suppression at higher pseudorapidity as well as the Cronin enhancement at mid- rapidity. Here we present the extension of this work to the more massive ion-ion collisions.

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arXiv2004

High Tranverse Momentum Suppression in Au+Au Collisions

Great interest has attached to recent Au+Au, E = 200 A GeV measurements at RHIC, obtained with the PHENIX, STAR, PHOBOS and BRAHMS detectors. For central collisions and vanishing pseudo-rapidity all experiments indicate a considerable lowering in charged particle production at mid to large transverse momenta. In the PHENIX experiment similar behavior has been reported for pi0 spectra. In a recent work on the presumably simpler D+Au interaction, to be considered perhaps as a tune-up for Au+Au, we reported on a hadronic cascade mechanism which can explain the observed but somewhat reduced pT suppression at higher pseudo rapidity as well as the Cronin enhancement at mid rapidity. Here we report on the extension of this work to the more massive ion-ion collisions.

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arXiv2004

Cronin Effect and High Transver Momentum Suppression in D+Au Collisions

Great interest has attached to recent D+Au, s^(1/2) = 200 A GeV data at RHIC, obtained with the BRAHMS detector. Between pseudorapidity eta=0 and eta=3.2 the appropriately defined ratio R[DAu/PP], comparing transverse momentum spectra of D+Au to P+P exhibits a steady decrease with eta. This diminuition is examined within a two-stage simulation, the last stage being a purely hadronic, reduced energy cascade. The result is an adequate description of the data including the so-called Cronin effect. Additionally there is clear evidence for suppression, in the second stage, of relatively high transverse momentum, eta=0, leading mesons, i.e. the Cronin effect, only near mid-rapidity, is appreciably muted by final state interactions.

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arXiv2003

Pentaquark as Kaon-Nucleon Resonance

Several recent experiments have reported evidence for a narrow feature in the K(+)-neutron system, an apparent resonant state ~ 100 MeV above threshold and with a width < 25 MeV. This state has been labelled as Theta(+) (previously as Z(*)), and because of the implied inclusion of a anti-strange quark, is referred to as a pentaquark, that is, five quarks within a single bag. We present an alternative explanation for such a structure, as a higher angular momentum resonance in the isospin zero K(+) -N system. One might call this an exit channel or a molecular resonance. In a non-relativistic potential model we find a possible candidate for the kaon-nucleon system with relative angular momentum L=3, while L=1 and 2 states possess centrifugal barriers too low to confine the kaon and nucleon in a narrow state at an energy so high above threshold. A rather strong state-dependence in the potential is essential, however, for eliminating an observable L=2 resonance at lower energies.

hep-ph↗

arXiv2003

Resonant State in Helium-4 Lambda

In a recent experiment E906 at the BNL-AGS, a search for light S=-2 hypernuclei, strong evidence was found for the nuclide Hydrogen-4 double Lambda. One of the most striking components of this data was the appearance of a narrow low-momentum pi- line at k(pi-) = 104-105 MeV/c. This was ascribed to the decay of Hydrogen-4 double Lambda into a resonant state in Helium-4 Lambda. The existence of such a state is shown to be plausible and its characteristics are delineated.

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arXiv2002

Soft Physics, Centrality and Multiplicity at RHIC

The inclusive spectra so far accumulated at the Relativistic Heavy Ion Collider (RHIC) at energies of $\sqrt{s} = 56, 130$ and 200 GeV are examined within the hadronic simulation LUCIFER. What emerges at this juncture is a comprehensive and clear picture of soft physics which apparently dominates the intermediate and later stages of the ion collisions. The focus is on energy and centrality dependence of the mid-rapidity charged spectra, using an analysis based for the most part on production and rescattering of intermediate generic resonances. The bosonic Rho and K(*)-like resonances, produced in initial nucleon-nucleon interactions and materialising only after some delay time, behave like an incompressible fluid with saturated number and energy density.

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arXiv2002

Multi-Quark Hadrons and S=-2 Hypernuclei

The general character of 4-quark (mesonic) and strange 6-quark (baryonic) quark systems is very briefly reviewed a la Jaffe, i.e. in the MIT bag, and so far still possibly viable candidates are indicated. Concentration is on S=-2 systems. Traditionally, one employs the (K^-,K^+) reaction on a relatively light target and hopes to retain two units of strangeness on a single final state fragment. Alternatively, heavy ion reactions can be used to produce Lambda-hyperons copiously and one seeks to observe coalescence of two of these particles into the lightest S=-2 nucleus, the H-dibaryon. The complications arising from the presence of a repulsive core in the baryon-baryon interaction on the production of the H are discussed. Also considered is the possible presence in the data from the AGS experiment E906, of slightly heavier S=-2 nuclei, in particular_{Lambda Lambda}^{4}H.

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arXiv2000

Inclusive Particle Spectra at RHIC

A simulation is performed of the recently reported data from PHOBOS at energies of 56 and 130 A GeV using the relativistic heavy ion cascade LUCIFER which had previously given a good description of the NA49 inclusive spectra at E=17.2 A GeV. The results compare well with these early measurements at RHIC.

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arXiv1999

An Update on NA50 and LUCIFER

Recent analysis of both new (1998) and old (1995,1996) data obtained by the NA50 Collaboration on J/Psi suppression in Pb+Pb are examined in light of our already existing calculations with the relativistic heavy ion simulation LUCIFER. In particular we comment on the unexplained change of transverse energy scale by NA50 and the apparent disappearance from the data of discontinuities in the suppression with transverse energy.

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arXiv1999

The H-Dibaryon and the Hard Core

The H dibaryon, a single, triply magic bag containing two up, two down and two strange quarks, has long been sought after in a variety of experiments. Its creation has been attempted in $K^-$, proton and most recently in relativistic heavy ion induced reactions. We concentrate on the latter, but our conclusions are more generally applicable. The two baryons coalescing to form the single dibaryon, likely $ΛΛ$ in the case of heavy ions, must penetrate the short range repulsive barrier which is expected to exist between them. We find that this barrier can profoundly affect the probability of producing the H state, should it actually exist.

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arXiv1998

Charmonium Production at the SPS

We reexamine the production of J/Psi and other charmonium states for a variety of target-projectile choices at the SPS, in particular for the interesting comparison between S+U at 200 GeV/c and Pb+Pb at 158 GeV/c as observed in the experiments NA38 and NA50 respectively. The result is a description of the NA38 and NA50 data in terms of a conventional, quasi-hadronic picture. The apparently anomalous suppression found in the most massive Pb+Pb system arises in the present simulation from three sources: destruction in the initial nucleon-nucleon cascade phase, use of coupled channels to exploit the larger breakup in the less bound Chi and Psi' states, and comover interaction in the final low energy phase.

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arXiv1998

J/Psi Suppression in Heavy Ion Collisions at the CERN SPS

We reexamine the production of J/Psi and other charmonium states for a variety of target-projectile choices at the SPS. For this study we use a newly constructed cascade code LUCIFER II, which yields acceptable descriptions of both hard and soft processes, specifically Drell-Yan and hidden charm production, and soft energy loss and meson production, at the SPS. Glauber calculations of other authors are redone, and compared directly to the cascade results. The modeling of the charmonium states differs from that of earlier workers in its unified treatment of the hidden charm meson spectrum, which is introduced from the outset as a set of coupled states. The result is a description of the NA38 and NA50 data in terms of a conventional hadronic picture. The apparently anomalous suppression found in the most massive Pb+Pb system arises from three sources: destruction in the initial nucleon-nucleon cascade, use of coupled channels to exploit the larger breakup in the less bound Chi and Psi' states, and comover interaction in the final low energy phase.

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arXiv1998

Strangeness Production and Ultrarelativistic Cascades

A two phase cascade, LUCIFER II, developed for the treatment of ultra high energy ion-ion collisions is applied to the production of strangeness at SPS energies $\sqrt{s}=17-20$. This simulation is able to simultaneously describe both hard processes such as Drell-Yan and slower, soft processes such as the production of light mesons, including strange mesons, by separating the dynamics into two steps, a fast cascade involving only nucleons in the original colliding relativistic ions followed, after an appropriate delay, by multiscattering of the resulting excited baryons and mesons produced virtually in the first step. No energy loss can take place in the short time interval over which the first cascade takes place. The chief result is a reconciliation of the important Drell-Yan measurements with the apparent success of standard cascades to describe the nucleon stopping and meson production in heavy ion experiments at the CERN SPS. A byproduct, obtained here in preliminary calculations, is a description of strangeness production in the collision of massive ions.

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