arXiv subjects

Spencer R. Klein

Publications and source records attributed to Spencer R. Klein.

77 records · Page 5Linked to original sources

arXiv2000

Nonlinear QED Effects in Heavy Ion Collisions

Peripheral collisions of relativistic heavy ions uniquely probe many aspects of QED. Examples include $e^+e^-$ pair production and nuclear excitation in strong fields. After discussing these reactions, I will draw parallels between $γ\to e^+e^-$ and $γ\to q\bar q$ and consider partly hadronic reactions. The scattered $q\bar q$ pairs are a prolific source of vector mesons, which demonstrate many quantum effects. The two ions are a two-source interferometer, demonstrating interference between meson waves. Multiple vector meson production will demonstrate superradiance, a first step toward a vector meson laser. Finally, I will discuss the experimental program planned at the RHIC and LHC heavy ion colliders.

physics.acc-ph↗

arXiv2000

Localized Beampipe Heating due to $e^-$ Capture and Nuclear Excitation in Heavy Ion Colliders

At heavy ion colliders, two major sources of beam loss are expected to be $e^+e^-$ production, where the $e^-$ is bound to one of the nuclei, and photonuclear excitation and decay via neutron emission. Both processes alter the ions charged to mass ratio by well defined amounts, creating beams of particles with altered magnetic rigidity. These beams will deposit their energy in a localized region of the accelerator, causing localized heating, The size of the target region depends on the collider optics. For medium and heavy ions, at design luminosity at the Large Hadron Collider, local heating may be more than an order of magnitude higher than expected. This could cause magnet quenches if the local cooling is inadequate. The altered-rigidity beams will also produce localized radiation damage. The beams could also be extracted and used for fixed target experiments.

physics.acc-ph↗

arXiv1999

Interference in Exclusive Vector Meson Production in Heavy Ion Collisions

Photons emitted from the electromagnetic fields of relativistic heavy ions can fluctuate into quark anti-quark pairs and scatter from a target nucleus, emerging as vector mesons. These coherent interactions are identifiable by final states consisting of the two nuclei and a vector meson with a small transverse momentum. The emitters and targets can switch roles, and the two possibilities are indistinguishable, so interference may occur. Vector mesons are negative parity so the amplitudes have opposite signs. When the meson transverse wavelength is larger than the impact parameter, the interference is large and destructive. The short-lived vector mesons decay before amplitudes from the two sources can overlap, and so cannot interfere directly. However, the decay products are emitted in an entangled state, and the interference depends on observing the complete final state. The non-local wave function is an example of the Einstein-Podolsky-Rosen paradox.

hep-ph↗

arXiv1999

Suppression of Bremsstrahlung and Pair Production due to Environmental Factors

The environment in which bremsstrahlung and pair creation occurs can strongly affect cross sections for these processes. Because ultra-relativistic electromagnetic interactions involve very small longitudinal momentum transfers, the reactions occur gradually, spread over long distances. During this time, even relatively weak factors can accumulate enough to disrupt the interaction. This review will discuss a variety of factors which can suppress bremsstrahlung and pair production, as well as related effects involving beamstrahlung and QCD processes. After surveying different theoretical approaches, experimental measurements from the early cosmic ray studies to the recent detailed measurements by the SLAC E-146 collaboration will be discussed.

hep-ph↗

arXiv1998

The LPM Effect: Comparing SLAC E-146 Data with Experiment

The suppression of photon bremsstrahlung due to a variety of in-medium effects is discussed. Different electrodynamic suppression effects are discussed, and compared with the related color analogs. Higher order effects are considered, and found to be important. Data from SLAC E-146 is discussed, and compared with theory. The effect of finite thickness targets is emphasized, since nuclear size is such an important limiting factor for the chromodynamics effects.

hep-ph↗