arXiv subjects

Kevin Haglin

Publications and source records attributed to Kevin Haglin.

14 recordsLinked to original sources

arXiv2004

Short-Lived Phi Mesons

We use effective hadronic field theory to study in-medium properties of the $ϕ$ meson. The dominant decay channels $ϕ\toK^{+}K^{-}$ and $ϕ\toπρ$ are modeled using an SU(3) chiral Lagrangian with normal and abnormal parities. The $ϕ$ self-energy is approximated to one-, two-, and even three-loop order in the strong coupling. Effects of modified spectral functions for $π$, $K$, $ρ$ and $ϕ$ are also included in the calculation. This allows us to study in-medium decay of phi mesons into (in-medium) kaon-pair daughters and (in-medium) $πρ$ pairs. The results point to the possibility of rather short-lived $ϕ$'s, short enough to decay inside the fireball in relativistic heavy ion collisions. Implications relevant for the NA49 and NA50 experimental results, recently dubbed the ``$ϕ$ puzzle'', are discussed.

nucl-th↗

arXiv2003

Using Conditional Phase Change Operations to Probe the Nature of Quantum Mechanical Systems

Recent developments in quantum computing suggest that it could be possible to make conditional changes to the state of a quantum mechanical system without resorting to classical observation. It is accomplished through collective response of atoms comprising a lattice for the system and involves relative phase adjustments only. We exploit this possibility and describe experimental designs that could help elucidate quantum mechanical properties of these systems and distinguish between interpretations.

quant-ph↗

arXiv2003

J/Psi Propagation in Hadronic Matter

We study J/$ψ$ propagation in hot hadronic matter using a four-flavor chiral Lagrangian to model the dynamics and using QCD sum rules to model the finite size effects manifested in vertex interactions through form factors. Charmonium breakup due to scattering with light mesons is the primary impediment to continued propagation. Breakup rates introduce nontrivial temperature and momentum dependence into the J/$ψ$ spectral function.

hep-ph↗

arXiv2000

Modeling J/psi Properties at Finite Temperature

We model J/psi using an effective lagrangian approach and calculate its spectral function in a gas of light mesons at finite temperature. We explore the hadronic landscape estimating cross sections for elastic and inelastic channels. Effects of form factors are tested in a general, but consistently gauge invariant manner. Relevance to heavy ion experiments is discussed.

nucl-th↗

arXiv1998

Phase space density and chiral symmetry restoration in relativistic heavy ion collisions

The effect of altered hadron masses is studied for its effect with regard to final-state hadronic observables. It is shown that the final phase space densities of pions and kaons, which can be inferred experimentally, are sensitive to in-medium properties of the excited matter at earlier stages of the collision, but that the sensitivity is significantly moderated by interactions that change the effective numbers of pions and kaons during the latter part of the collision.

nucl-th↗

arXiv1998

Exploring the nuclear pion dispersion relation through the anomalous coupling of photon to photon and neutral pion

We investigate the possibility of measuring the pion dispersion relation in nuclear matter through the anomalous coupling in the reaction γ- γ' π_0. It is shown that this reaction permits the study of pionic modes for space-like momenta. If the pion is softened in nuclear matter due to mixing with the delta-hole state, significant strength for this reaction is expected to move into the space-like region. Competing background processes are evaluated, and it is concluded that useful insight can be obtained experimentally, but only through a difficult exclusive measurement.

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arXiv1996

Coherent Pion Pairs from Heavy-Ion Collisions

The degree to which a nucleus can act as a source for coherent pion pairs is investigated for intermediate-energy heavy-ion collisions. Creation through both isovector and isoscalar channels is considered. Two experimental signals are proposed for evidence of two-pion coherent production, two-pion enhancement and the focusing of outgoing pions along the beam axis.

nucl-th↗

arXiv1995

Higher excitations of $ω$ and $ϕ$ in dilepton spectra

We consider lepton pair production via two-hadron annihilation through various isoscalar vector mesons within hot, baryon-free matter. This is tantamount to constructing effective form factors which we model using a vector-meson-dominance approach and compare with experiment. In particular, we consider the reactions $πρ\to e^+e^-$ and $\bar K K^{*}(892)$ + c.c. $\to e^+e^-$. We find that $ω(1390)$ and $ϕ(1680)$ are visible in the mass spectrum for the thermal production rate above the $π^{+}π^{-} \to e^+e^-$ tail and even above the $πa_{1}\to e^+e^-$ results---both of which were considered important in their respective mass regions.

nucl-th↗

arXiv1995

Another Look at ``soft'' lepton pair production in nucleon-nucleon bremsstrahlung

We compare different formalisms for the calculation of lepton pair emission in hadron-hadron collisions and discuss the consequences of the approximations inherent to each of them. Using a Lorentz-covariant and gauge-invariant formalism proposed by Lichard, we calculate lepton pair emission via bremsstrahlung in proton-proton and neutron-proton reactions at energies between 1 and 5 GeV to leading order in the virtual photon four-momentum. These new results suggest that some previous bremsstrahlung calculations based on varieties of the soft-photon approximation might have somewhat overestimated the DLS low-mass dilepton cross sections. We find that the respective intensities of dilepton production through $p p$ and $n p$ bremsstrahlung are energy-dependent and become comparable at $E_{\rm kin} \agt $ 2 GeV. We also calculate the polar angle anisotropy of the lepton spectrum.

nucl-th↗

arXiv1994

Collision rates for $\bboxρ$, $\bboxω$ and $\bboxϕ$ mesons at nonzero temperature

The $ω$ and $ϕ$ mesons are exceptionally narrow in vacua being about 8 and 4 MeV. At finite temperature they will scatter with other hadrons in their approach to equilibrium and thereafter. These dynamics induce broadening to the already unstable vector mesons which is calculated in the framework of relativistic kinetic theory. A rather complete set of low-lying mesons provide reaction partners whose interactions are modeled using effective Lagrangians. Collision rates for $ρ$ and $ω$ are found to be $\sim$ 100 MeV at $T$=200 MeV while the rate for $ϕ$ is $\sim$ 25 MeV. Corresponding mean free paths are about 1 and 4 fm! Possible observable consequences are discussed.

nucl-th↗

arXiv1994

Photons from axial-vector radiative decay in a hadron gas

Strange and non-strange axial-vector meson radiative decays contribute to photon production in hadron gas. One- and two-hadron radiative decay modes of $b_{1}(1235)$, $a_{1}(1260)$ and $K_{1}(1270)$ are studied. At 200 MeV temperature and for a narrow range in photon energies they contribute more to the net thermal photon production rate than $πρ\rightarrow πγ$, $ππ\rightarrow ργ$ or $ρ\rightarrowππγ$. They provide significant contribution to the rate for photon energies as high as 1.5--2.0 GeV. For higher energies they are less important.

nucl-th↗

arXiv1994

On the mean free paths of pions and kaons in hot hadronic matter

Pion and kaon mean free paths within a thermal hadronic background are calculated using relativistic kinetic theory. Free cross sections are used which include contributions from $ρ$, $K^{*}$, $Δ$ and heavier resonances. Given pion to baryon ratios appropriate for the breakup stage of a $200\cdot A$GeV relativistic-heavy-ion collision, we find for temperatures less than 100 MeV, kaons have a shorter mean free path than pions, while for higher breakup temperatures the reverse is true. Since breakup temperatures should be in the neighborhood of 100 MeV, this suggests that kaon interferometry samples the same emission distribution as pion interferometry.

nucl-th↗

arXiv1993

Dilepton Production in Nucleon-Nucleon Reactions With and Without Hadronic Inelasticities

We calculate elementary proton-proton and neutron-proton bremsstrahlung and their contribution to the $e^+e^-$ invariant mass distribution. At 4.9 GeV, the proton-proton contribution is larger than neutron-proton, but it is small compared to recent data. We then make a first calculation of bremsstrahlung in nucleon-nucleon reactions with multi-hadron final states. Again at 4.9 GeV, the many-body bremsstrahlung is larger than simple nucleon-nucleon bremsstrahlung by more than an order of magnitude in the low-mass region. When the bremsstrahlung contributions are summed with Dalitz decay of the $η$, radiative decay of the $Δ$ and from two-pion annihilation, the result matches recent high statistics proton-proton data from the Dilepton Spectrometer collaboration.

nucl-th↗

arXiv1993

Measuring velocity ratios with correlation functions

We show how to determine the ratio of the transverse velocity of a source to the velocity of emitted particles, using split-bin correlation functions. The technique is to measure $S_2$ and $S_2^ϕ$, subtract the contributions from the single-particle distribution, and take the ratio as the bin size goes to zero. We demonstrate the technique for two cases: each source decays into two particles, and each source emits a large number of particles.

hep-ph↗