arXiv subjects

Kevin L. Haglin

Publications and source records attributed to Kevin L. Haglin.

12 recordsLinked to original sources

arXiv2023

Uncertainty Principles for Teaching Laboratories

Educators must make decisions about learner expectations and skills on which to focus when it comes to laboratory activities. There are various approaches but the general pattern is to encourage students to measure ordered pairs, plot a graph to establish linear dependence, and then compute the slope of the best-fit line for an eventual scientific conclusion. To assist educators when they also want to include slope uncertainty dependent upon measurement uncertainty as part of the expected analysis, we demonstrate a physical approach so that both educators and their students have a convenient roadmap to follow. A popular alternative that educators often choose is to rely solely on statistical metrics to establish the tolerance of the technique, but we argue the statistical strategy can distract students away from the true meaning of the uncertainty that is inherent in the act of making the measurements. We will carry these measurement error bars from their points of origin through the regression analysis to consistently establish the physical error bars for the slope and the intercept. We then demonstrate the technique using an introductory physics experiment with a purpose of measuring the speed of sound in air.

physics.ed-ph↗

arXiv2010

Point Charge Dynamics Near a Grounded Conducting Plane

The classic image problem in electromagnetism involves a grounded infinite conducting plane and a point charge. The force of attraction between the point charge and the plane is identified using an equivalent-field picture of an image charge with opposite sign equidistant behind the plane resulting in a 1/{\it r}$^{\rm 2}$ force of attraction between the original charge and the plane. If the point charge is released from rest it will reach the plane in a time $τ$. This time $τ$ has not been calculated correctly up to now. Clarification of the inconsistency is presented along with a correct solution to the classic image problem. Other electromagnetism problems are mentioned with attractive 1/{\it r}$^{\it n}$ forces (where {\it n} $\ge$ 1). Such situations arise between a point charge and a line charge (1/{\it r}), between a line charge and a point dipole (1/{\it r}$^{2}$), between a point charge and a point dipole (1/{\it r}$^{3})$, and between a point dipole and a second point dipole (1/{\it r}$^{4}$).

physics.class-ph↗

arXiv2004

Phi Meson Propagation and Decay at Finite Temperature

We study spectral properties of the phi meson at finite temperature using an effective Lagrangian together with finite-temperature field theory as a basis for modeling. General field-theoretic arguments are then used to establish the lifetime of the phi in hot hadronic matter. We find from the model, and we therefore propose a scenario in which, the phi decays inside the fireball. Early decays into $μ^{+}μ^{-}$ occur at high temperature while measurable hadronic decays into $K^{+}K^{-}$ (not suffering rescattering) occur at freezeout, where flow could be substantial. These results provide a consistent picture, if not possible interpretation of the NA49 and NA50 data from CERN.

nucl-th↗

arXiv2003

Electromagnetic radiation from relativistic nuclear collisions

We review some of the results obtained in the study of the production of electromagnetic radiation in relativistic nuclear collisions. We concentrate on the emission of real photons and dileptons from the hot and dense strongly interacting phases of the reaction. We examine the contributions from the partonic sector, as well as those from the nonperturbative hadronic sector. We examine the current data, some of the predictions for future measurements, and comment on what has been learnt so far.

hep-ph↗

arXiv2003

Flow Buildup in a Mixed Phase of Quark-Gluon Plasma Plus Hadrons

Transport processes are considered for their abilities to generate flow in a mixed-phase system of hadrons plus quark-gluon plasma exhibiting temperature and density gradients. Diffusive mechanisms are found to be the leading sources. Even after overcoming viscous effects, conductive and diffusive forces generate flow velocities for pions in a model using kinetic theory to within fifteen percent of light speed. Since such flow is not observed, this could possibly rule out the mixed phase in the evolution of high energy heavy ion collisions.

hep-ph↗

arXiv2002

Structure and Dynamics of Charmonium

We apply a confining q\bar{q} potential to charmonium and open charm in order to model wave functions and to begin studying structure. Results (in momentum space) provide form-factor input to a four-flavor effective chiral Lagrangian which models dynamics of charmonium in hot hadronic matter. Estimates are made for J/ψdissociation cross sections and rates within a fireball. Our study attempts to improve on previous comover suppression models since it includes gauge-invariant form-factor formalism constrained by quark-model phenomenology.

nucl-th↗

arXiv2002

On the Penetrating Nature of Electromagnetic Probes

We establish the extent to which photons and dileptons are penetrating probes of hot hadronic matter by computing mean free paths. Absorption is indeed negligible for real photons as mean free paths are roughly tenths of \AAngströms. However, vector dominance effects, which provide rich structure in virtual photon mass spectra, introduce nonnegligible reabsorption and rehadronization resulting in mean free paths of the order of tens of femtometers. Consequences are illustrated by considering the net dilepton yield near the rho peak via thermal ππannihilation from a short-lived hadronic fireball. Results suggest that disappearance of the rho in heavy-ion collisions can be due in part to reabsorption/rehadronization rather than solely due to collective effects.

nucl-th↗

arXiv2000

Hadronic interactions of the J/psi

We calculate the cross sections for reactions of the J/psi with light mesons. We also evaluate its finite temperature spectral function. We investigate separately the role of elastic and inelastic channels and we compare their respective importance. We describe J/psi absorption channels that have not been considered previously to our knowledge. The relevance of our study to heavy ion collisions is discussed.

nucl-th↗

arXiv2000

Charmonium dissociation in hadronic matter

Production of J/$ψ$ from nucleus-nucleus reactions depends sensitively on the dissociation cross section with light hadrons. Effective lagrangian methods are used to describe the hadronic degrees of freedom, including strangeness and charm. Cross sections with pions, rho mesons, kaons and nucleons having magnitudes 4--8 mb are found, and with steep thresholds. This, folded with thermal momentum distributions for the scattering partners, suggests a mean dissociation lifetime $\simeq$ 20 fm/c. Therefore, the ``abnormal'' J/$ψ$ suppression seen in recent Pb+Pb experiments seems to owe to expected hadron kinetics.

nucl-th↗

arXiv1997

Collision Broadening of the Phi Meson in Baryon Rich Hadronic Matter

Phi meson-baryon cross sections, estimated within a one-boson-exchange model, serve as input for a calculation of the collision rates in hot hadronic matter. We find that the width of the ϕmeson is modified through collisions with baryons by 1-10 MeV at 160 MeV temperature depending on the baryon fugacity. Thermalization of the ϕin high energy heavy ion collisions is discussed.

nucl-th↗

arXiv1996

Excess electron pairs from heavy-ion collisions at CERN and a more complete picture of thermal production

The low-mass dielectron signal from heavy-ion collisions at the CERN--SPS reported by the {\em CERES} collaboration is in excess of estimated hadronic decays suggestive of possible contribution from two-pion annihilation or other hadronic reactions. In the absence of dramatic medium modifications, annihilation alone is unable to account for the data. We explore the role of pion plus resonance scattering [$πρ\to a_{1}(1260) \to πe^+e^-$] which has favorable kinematics to populate masses between $2m_π$ and $m_ρ$. While it seems to account for some of the remaining excess beyond annihilation, it fails to allow quantitative interpretation of data.

nucl-th↗

arXiv1994

Properties of the phi meson at finite temperature

We calculate the $ϕ$-meson propagator at finite temperature at the one--loop order. The real and imaginary parts are studied separately in full kinematic ranges. From this activity we investigate how temperature affects such things as decay widths and dispersion relations. {}From here we estimate the thermal rate of lepton pair radiation in a hadron gas proceeding through $K^{+}K^{-}\to ϕ\to \ell^{+}\ell^{-}$ and $πρ\to ϕ\to \ell^{+}\ell^{-}$. We find several interesting things. From the dispersion relations we learn the effective mass calculated this way increases with temperature as does the partial width, but only slightly. At $T=200$ MeV, the mass increases by $\sim$ 4 MeV and the partial width increases by 34\%. Polarizations are indistinguishable for practical purposes.

nucl-th↗