122902661
Inelastic alpha scattering studies of the low-energy octupole resonance
Beams of 96 and 115 MeV $\ensuremath{\alpha}$ particles have been used to study the distribution of isoscalar octupole strength in 18 nuclei from $^{40}\mathrm{Ca}$ to $^{208}\mathrm{Pb}$. A prominent broad peak ($\ensuremath{\Gamma}\ensuremath{\sim}2.5$ MeV) is observed at ${E}_{x}\ensuremath{\sim}\frac{30}{{A}^{\frac{1}{3}}}$ MeV in nuclei from $^{66}\mathrm{Zn}$ to $^{197}\mathrm{Au}$. No broad peak is observed in this excitation energy range in $^{208}\mathrm{Pb}$ or $^{40}\mathrm{Ca}$ and lighter nuclei. The oscillatory angular distributions of the ($\ensuremath{\alpha}, {\ensuremath{\alpha}}^{\ensuremath{'}}$) reaction exciting this peak are in excellent agreement with $l=3$ distorted-wave Born approximation calculations. Studies of the angular range from ${\ensuremath{\sigma}}_{\mathrm{lab}}=3.5\ifmmode^\circ\else\textdegree\fi{} \mathrm{to} 6\ifmmode^\circ\else\textdegree\fi{}$ in $^{116}\mathrm{Sn}$ indicate very little contribution from $l=1$ strength. Energy- weighted sum rule fractions for this low-energy octupole resonance are generally in the range from 15% to 20%; this corresponds to \textonehalf{} to $\frac{2}{3}$ of the expected $1\ensuremath{\hbar}\ensuremath{\omega}$ octupole strength. The overall distribution of octupole strength in spherical nuclei, including the absence of the low-energy octupole resonance in $^{40}\mathrm{Ca}$ and $^{208}\mathrm{Pb}$, is in very good agreement with random-phase approximation calculations. The low-energy octupole resonance undergoes a pronounced change in structure in soft-vibrational and deformed nuclei. Theoretical calculations for the low-energy octupole resonance in $^{154}\mathrm{Sm}$ account qualitatively for the data.
124330538
Giant resonances observed in the scattering of 96- and 115-MeV alpha particles
Beams of 96- and 115-MeV $alpha$ particles were used to study the giant resonance region in 27 nuclei ranging from $sup 14$N to $sup 208$Pb. A prominent broad (GAMMA=3--7 MeV) peak is present in the spectra at an excitation energy of approx.63/A$sup 1$/$sup 3$ MeV for all nuclei studied with A> or =36. No such prominent peak is apparent for A<32. The angular distributions of the peak are characterized by an oscillatory behavior which is quite different from the monotonic behavior of the background. Distorted wave calculations with L=2 reproduce the experimental angular distributions quite well for most of the nuclei. Energy-weighted sum rule fractions range from 30--50% for the lighter targets to near 100% for the heavier targets. Distorted wave calculations with a breathing mode (L=0) form factor fail to reproduce the observed resonance strength by about a factor of 3 for all targets. The width of the peak is smallest for the closed shell nuclei $sup 40$Ca, $sup 90$Zr, $sup 144$Sm, and $sup 208$Pb. A small but significant broadening is observed in the rare-earth region of deformed nuclei. The giant dipole resonance is not appreciably excited for any of the targets. (AIP)
18546888
A high-energy nuclear database proposal
We propose to develop a high-energy heavy-ion experimental database and make it accessible to the scientific community through an on-line interface. This database will be searchable and cross-indexed with relevant publications, including published detector descriptions. Since this database will be a community resource, it requires the high-energy nuclear physics community’s financial and manpower support. This database should eventually contain all published data from the Bevalac, AGS and SPS to RHIC and LHC energies, proton-proton to nucleus-nucleus collisions as well as other relevant systems, and all measured observables. Such a database would have tremendous scientific payoff as it makes systematic studies easier and allows simpler benchmarking of theoretical models to a broad range of old and new experiments. Furthermore, there is a growing need for compilations of high-energy nuclear data for applications including stockpile stewardship, technology development for inertial confinement fusion and target and source development for upcoming facilities such as the Next Linear Collider. To enhance the utility of this database, we propose periodically performing evaluations of the data and summarizing the results in topical reviews.
119488847
Scintillating fiber hodoscope for a bremsstrahlung luminosity monitor at an electron–positron collider
The performance of a scintillating fiber (2 mm diameter) position sensitive detector (4.8×4.8 cm2 active area) for the single bremsstrahlung luminosity monitor at the VEPP‐2M electron‐positron collider in Novosibirsk, Russia is described. Custom electronics is triggered by coincident hits in the Y and Y planes of 24 fibers each, and reduces 64 photomultiplier signals to a 10‐bit (X,Y) address. Hits are accumulated (10 kHz) in memory and display (few Hz) the VEPP‐2M collision vertex. Fitting the strongly peaked distribution (∼3–4 mm at 1.6 m from the collision vertex of VEPP‐2M) to the expected QED angular distribution yields a background in agreement with an independent determination of the VEPP‐2M luminosity.
10664239
Rates and Characteristics of Intermediate Mass Ratio Inspirals Detectable by Advanced LIGO
Gravitational waves (GWs) from the inspiral of a neutron star (NS) or stellar-mass black hole (BH) into an intermediate-mass black hole (IMBH) with mass M � 50 350 Mmay be detectable by the planned advanced generation of ground-based GWinterferometers. Such intermediate mass ratio inspirals (IMRIs) are most likelyto be found in globular clusters. We analyze four possible IMRI formation mechanisms: (1) hardening of an NS-IMBH or BH-IMBH binary via three-body interactions, (2) hardening via Kozai resonance in a hierarchical triple system, (3) direct capture, and (4) inspiral of a CO from a tidally captured main-sequence star; we also discuss tidal effects when the inspiraling object is an NS. For each mechanism we predict the typical eccentricities of the resulting IMRIs. We find that IMRIs will have largely circularized by the time they enter the sensitivity band of ground-based detec- tors. Hardening of a binary via three-body interactions, which is likely to be the dominant mechanism for IMRI for- mation,yieldseccentricitiesunder10 � 4 whentheGWfrequencyreaches10Hz.EvenamongIMRIsformedviadirect captures, which can have the highest eccentricities, around 90% will circularize to eccentricities under 0.1 before the GW frequency reaches 10 Hz. We estimate the rate of IMRI coalescences in globular clusters and the sensitivity of a network of three Advanced LIGO detectors to the resulting GWs. We show that this detector network may see up to tens of IMRIs per year, although rates of one to a few per year may be more plausible. We also estimate the loss in signal-to-noise ratio that will result from using circular IMRI templates for data analysis and find that, for the eccen- tricities we expect, this loss is negligible. Subject headingg black hole physics — globular clusters: general — gravitational waves
1576896
Comparison of high-accuracy numerical simulations of black-hole binaries with stationary-phase post-Newtonian template waveforms for initial and advanced LIGO
We study the effectiveness of stationary-phase approximated post-Newtonian waveforms currently used by ground-based gravitational-wave detectors to search for the coalescence of binary black holes by comparing them to an accurate waveform obtained from numerical simulation of an equal-mass non-spinning binary black hole inspiral, merger and ringdown. We perform this study for the initial- and advanced-LIGO detectors. We find that overlaps between the templates and signal can be improved by integrating the match filter to higher frequencies than used currently. We propose simple analytic frequency cutoffs for both initial and advanced LIGO, which achieve nearly optimal matches, and can easily be extended to unequal-mass, spinning systems. We also find that templates that include terms in the phase evolution up to 3.5 post-Newtonian (pN) order are nearly always better, and rarely significantly worse, than 2.0 pN templates currently in use. For initial LIGO we recommend a strategy using templates that include a recently introduced pseudo-4.0 pN term in the low-mass (M ≤ 35 M☉) region, and 3.5 pN templates allowing unphysical values of the symmetric reduced mass η above this. This strategy always achieves overlaps within 0.3% of the optimum, for the data used here. For advanced LIGO we recommend a strategy using 3.5 pN templates up to M = 12 M☉, 2.0 pN templates up to M = 21 M☉, pseudo-4.0 pN templates up to 65 M☉, and 3.5 pN templates with unphysical η for higher masses. This strategy always achieves overlaps within 0.7% of the optimum for advanced LIGO.
16460087
Three-Dimensional Imaging Analysis of Two-Particle Correlations in Heavy-Ion Reactions
We report an extension of the source imaging method for imaging full three-dimensional sources from three-dimensional like-pair correlations. Our technique consists of expanding the correlation data and the underlying source function in spherical harmonics and inverting the resulting system of one-dimensional integral equations. With this method of attack, we can image the source function quickly, even with the extremely large data sets common in three-dimensional analyses. We apply our method to the recently measured E859 un-Coulomb corrected data.