A more effective coordinate system for parameter estimation of precessing compact binaries from gravitational waves

Ground-based gravitational wave detectors are sensitive to a narrow range of frequencies, effectively taking a snapshot of merging compact-object binary dynamics just before merger. We demonstrate that by adopting analysis parameters that naturally characterize this 'picture', the physical parameters of the system can be extracted more efficiently from the gravitational wave data, and interpreted more easily. We assess the performance of MCMC parameter estimation in this physically intuitive coordinate system, defined by (a) a frame anchored on the binary's spins and orbital angular momentum and (b) a time at which the detectors are most sensitive to the binary's gravitational wave emission. Using anticipated noise curves for the advanced-generation LIGO and Virgo gravitational wave detectors, we find that this careful choice of reference frame and reference time significantly improves parameter estimation efficiency for BNS, NS-BH, and BBH signals.Comment: 11 pages, 5 figures, submitted to Phys. Rev.

Sensitivity of dark matter dectectors to SUSY dark matter

ABSTRACT The sensitivity of dark matter detectors to the lightest neutralino ({\tilde {Z}_1}) is considered within the framework of supergravity grand unification with radiative breaking of SU(2)xU(1). The relic density of the {\tilde {Z}_1} is constrained to obey 0.10 \leq \Omega_{\tilde {Z}_1}h^2 \leq 0.35, consistent with COBE data and current measurements of the Hubble constant. Detectors can be divided into two classes: those most sensitive to spin dependent incoherent scattering of the {\tilde {Z}_1} (e.g. CaF_2) and those most sensitive to spin independent coherent scattering (high A nuclei e.g. Pb). The parameter space is studied over the range of 100GeV \leq m_0, m_{\tilde {g}} \leq 1~TeV; 2 \leq tan\beta \leq 20; and -2 \leq A_t/m_0 \leq 3 and it is found that the latter type detector is generally more sensitive than the former type. Thus at a sensitivity level of R \geq 0.1 events/kg da, a lead detector could scan roughtly 30\% of the ~parameter space studied, and an increase of ~this sensitivity by a factor of 10 ~would lead to coverage of about 70\% of the parameter space. Dark matter detectors are in general more sensitive to the high tan\beta, low m_{\tilde {g}} and low m_0 parts of the parameter space. The conditions of radiative breaking of SU(2)xU(1) enter importantly in analysing the efficiency of dark matter detectors

Detecting supersymmetric Q-balls with neutron stars

Supersymmetric Q-balls trapped in neutron stars or white dwarfs may cause the stars to explode. Trapping of Q-balls in neutron stars is shown to be less likely, but trapping in neutron star progenitors more likely than hitherto assumed, making neutron stars very sensitive Q-ball "detectors". White dwarfs only trap potentially dangerous Q-balls in a narrow parameter range.Comment: 6 pages, 2 figures, accepted for publication in Physics Letters

Gravitational-Wave Stochastic Background from Kinks and Cusps on Cosmic Strings

We compute the contribution of kinks on cosmic string loops to stochastic background of gravitational waves (SBGW).We find that kinks contribute at the same order as cusps to the SBGW.We discuss the accessibility of the total background due to kinks as well as cusps to current and planned gravitational wave detectors, as well as to the big bang nucleosynthesis (BBN), the cosmic microwave background (CMB), and pulsar timing constraints. As in the case of cusps, we find that current data from interferometric gravitational wave detectors, such as LIGO, are sensitive to areas of parameter space of cosmic string models complementary to those accessible to pulsar, BBN, and CMB bounds.Comment: 24 pages, 3 figure

Neutralino Proton Cross Sections In Supergravity Models

The neutralino-proton cross section is examined for supergravity models with R-parity invariance with universal and non-universal soft breaking. The region of parameter space that dark matter detectors are currently (or will be shortly) sensitive i.e. $(0.1-10)\times 10^{-6}$ pb, is examined. For universal soft breaking (mSUGRA), detectors with sensitivity $\sigma_{\tilde{\chi}_{1}^{0}-p} \geq 1 \times 10^{-6}$ pb will be able to sample parts of the parameter space for $\tan \beta \stackrel{>}{\sim} 25$. Current relic density bounds restrict $m_{\tilde{\chi}_{1}^{0}} \leq 120$ GeV for the maximum cross sections, which is below where astronomical uncertainties about the Milky Way are relevant. Nonuniversal soft breaking models can allow much larger cross sections and can sample the parameter space for $\tan \beta \stackrel{>}{\sim} 4$. In such models, $m_0$ can be quite large reducing the tension between proton decay bounds and dark matter analysis. We note the existance of two new domains where coannihilation effects can enter, i.e. for mSUGRA at large $\tan \beta$, and for nonuniversal models with small $\tan \beta$.Comment: 22 pages, latex, 18 figure

Neutralino Event Rates In Dark Matter Detectors

The expected event rates for ${\tilde Z_{1}}$ dark matter for a variety of dark matter detectors are studied over the full parameter space with tan $\beta\leq$ 20 for supergravity grand unified models. Radiative breaking constraints are implemented and effects of the heavy netural Higgs included as well as loop corrections to the neutral Higgs sector. The parameter space is restricted so that the ${\tilde Z_{1}}$ relic density obeys 0.10 $\leq\Omega_{\tilde Z_{1}}h^2\leq 0.35$, consistent with the COBE data and astronomical determinations of the Hubble constant. It is found that the best detectors sensitive to coherrent ${\tilde Z_{1}}$ scattering (e.g. Pb) is about 5-10 more sensitive than those based on incoherrent spin dependent scattering (e.g. CaF). In general, the dark matter detectors are most sensistive to the large tan $\beta$ and small $m_o$ and $m_{\tilde g}$ sector of the parameter space.Comment: Plain Tex file, 14 pages, 4 figures avalaible upon reques

Secure gated detection scheme for quantum cryptography

Several attacks have been proposed on quantum key distribution systems with gated single-photon detectors. The attacks involve triggering the detectors outside the center of the detector gate, and/or using bright illumination to exploit classical photodiode mode of the detectors. Hence a secure detection scheme requires two features: The detection events must take place in the middle of the gate, and the detector must be single-photon sensitive. Here we present a technique called bit-mapped gating, which is an elegant way to force the detections in the middle of the detector gate by coupling detection time and quantum bit error rate. We also discuss how to guarantee single-photon sensitivity by directly measuring detector parameters. Bit-mapped gating also provides a simple way to measure the detector blinding parameter in security proofs for quantum key distribution systems with detector efficiency mismatch, which up until now has remained a theoretical, unmeasurable quantity. Thus if single-photon sensitivity can be guaranteed within the gates, a detection scheme with bit-mapped gating satisfies the assumptions of the current security proofs.Comment: 7 pages, 3 figure