Search Results (151 total)

We extend previous work on the minimal D-term inflation model modified by right-handed (RH) sneutrino fields to include additional inflaton-sector supergravity corrections and two-field inflation effects. We show that supergravity corrections simultaneously allow n_s to be within 3-year Wilkinson Microwave Anisotropy Probe limits and the cosmic string contribution to the cosmic microwave background (CMB) power spectrum to be less than 5%. For gauge coupling g≤1, the CMB contribution from cosmic strings is predicted to be at least 1% while the spectral index is predicted to be less than 0.968 for a CMB string contribution less than 5%. Treating the inflaton-RH sneutrino system as a two-field inflation model, we show that the time-dependence of the RH sneutrino field strongly modifies the single-field results for values of RH sneutrino mass m_Φ>0.1H. The running spectral index is α≈-0.0002 when m_Φ<0.1H but increases to positive values as m_Φ/H increases, with α>0.008 for m_Φ>1.0H.

We present an analytical study of the standard two-party deterministic dense-coding protocol, under which communication of perfectly distinguishable messages takes place via a qudit from a pair of nonmaximally entangled qudits in a pure state |ψ⟩. Our results include the following: (i) We prove that it is possible for a state |ψ⟩ with lower entanglement entropy to support the sending of a greater number of perfectly distinguishable messages than one with higher entanglement entropy, confirming a result suggested via numerical analysis in Mozes [Phys. Rev. A 71, 012311 (2005)]. (ii) By explicit construction of families of local unitary operators, we verify, for dimensions d=3 and d=4, a conjecture of Mozes about the minimum entanglement entropy that supports the sending of d+j messages, 2≤j≤d−1; moreover, we show that the j=2 and j=d−1 cases of the conjecture are valid in all dimensions. (iii) Given that |ψ⟩ allows the sending of K messages and has sqrt[λ₀] as its largest Schmidt coefficient, we show that the inequality λ₀≤d/K, established by Wu [Phys. Rev. A 73, 042311 (2006)], must actually take the form λ₀<d/K if K=d+1, while our constructions of local unitaries show that equality can be realized if K=d+2 or K=2d−1.

We present a new measurement of the difference between the nucleon strange and antistrange quark distributions from dimuon events recorded by the NuTeV experiment at Fermilab. This analysis is the first to use a complete next to leading order QCD description of charm production from neutrino scattering. Dimuon events in neutrino deep inelastic scattering allow direct and independent study of the strange and antistrange content of the nucleon. We find a positive strange asymmetry with a significance of 1.6σ. We also report a new measurement of the charm mass.

We used our (perviously described) system for high sensitivity measurements of β-delayed α-particle emission of light nuclei to measure upper limits of the branching ratios of the first-forbidden rank-one β decay of the 2⁺ ground state of ²⁰F to the 3^-,5.62 MeV, and 1^-,5.79 MeV excited states of ²⁰Ne to be 1.5×10^-6 and 7×10^-7, respectively. These limits are more than a factor of 300 smaller than previously measured. The obtained ft values are at least a factor of 10 smaller than that of the first-forbidden rank-zero β decay to the 2^- state at 4.97 MeV in ²⁰Ne, whose branching ratio was also measured to be 1.2(6)×10^-4, in agreement with the precise value obtained by Alburger and Warburton of 0.90(4)×10^-4.

We measured the β-delayed α-particle emission spectrum of ¹⁶N with a sensitivity for β-decay branching ratios of the order of 10^-10. The ¹⁶N nuclei were produced using the d(¹⁵N,¹⁶N)p reaction with 70 MeV ¹⁵N beams and a deuterium gas target 7.5 cm long at a pressure of 1250 torr. The ¹⁶N nuclei were collected (over 10 s) using a thin aluminum foil with an areal density of 180 μg/cm² tilted at 7^° with respect to the beam. The activity was transferred to the counting area by means of a stepping motor in less than 3  s with the counting carried out over 8  s. The β-delayed α-particles were measured using a time-of-flight method to achieve a sufficiently low background. Standard calibration sources (¹⁴⁸Gd, ²⁴¹Am, ^208,209Po, and ²²⁷Ac) as well as α particles and ⁷Li from the ¹⁰B(n,α)⁷Li reaction were used for an accurate energy calibration. The energy resolution of the catcher foil (180–220 keV) was calculated and the time-of-flight resolution (3–10 nsec) was measured using the β-delayed α-particle emission from ⁸Li that was produced using the d(⁷Li,⁸Li)p reaction with the same setup. The line shape was corrected to account for the variation in the energy and time resolution and a high statistics spectrum of the β-delayed α-particle emission of ¹⁶N is reported. However, our data (as well as earlier Mainz data and unpublished Seattle data) do not agree with an earlier measurement of the β-delayed α-particle emission of ¹⁶N taken at TRIUMF after averaging over the energy resolution of our collection system. This disagreement, among other issues, prohibits accurate inclusion of the f-wave component in the R-matrix analysis.

This Letter reports results from the MINOS experiment based on its initial exposure to neutrinos from the Fermilab NuMI beam. The rates and energy spectra of charged current ν_μ interactions are compared in two detectors located along the beam axis at distances of 1 and 735 km. With 1.27×10²⁰ 120 GeV protons incident on the NuMI target, 215 events with energies below 30 GeV are observed at the Far Detector, compared to an expectation of 336±14 events. The data are consistent with ν_μ disappearance via oscillations with |Δm₃₂²|=2.74_-0.26^+0.44×10^-3  eV² and sin⁡²(2θ₂₃)>0.87 (68% C.L.).

Supergravity corrections due to the energy density of a right-handed sneutrino can generate a negative mass squared for the inflaton, flattening the inflaton potential and reducing the spectral index and inflaton energy density. For the case of D-term hybrid inflation, we show that the spectral index can be lowered from the conventional value n=0.98 to a value within the range favored by the latest WMAP analysis, n=0.951_-0.019^+0.015. The modified energy density is consistent with nonobservation of cosmic strings in the CMB if n<0.946. The WMAP lower bound on the spectral index implies that the D-term cosmic string contribution may be very close present CMB limits, contributing at least 5% to the CMB multipoles.

The NuTeV experiment at Fermilab has obtained a unique high-statistics sample of neutrino and antineutrino interactions using its high-energy sign-selected beam. We present a measurement of the differential cross section for charged-current neutrino and antineutrino scattering from iron. We determine the relative ν̅ to ν cross section, r=σ^ν̅ /σ^ν, at high energy with errors a factor of 2 smaller than the previous world average. Structure functions, F₂(x,Q²) and xF₃(x,Q²), are determined by fitting the inelasticity, y, dependence of the cross sections. This measurement has significantly improved systematic precision as a consequence of more precise understanding of hadron and muon energy scales.

The complete 5.4 kton MINOS far detector has been taking data since the beginning of August 2003 at a depth of 2070 meters water-equivalent in the Soudan mine, Minnesota. This paper presents the first MINOS observations of ν_μ and ν̅ _μ charged-current atmospheric neutrino interactions based on an exposure of 418 days. The ratio of upward- to downward-going events in the data is compared to the Monte Carlo expectation in the absence of neutrino oscillations, giving R_up/down^data/R_up/down^MC=0.62_-0.14^+0.19(stat.)±0.02(sys.). An extended maximum likelihood analysis of the observed L/E distributions excludes the null hypothesis of no neutrino oscillations at the 98% confidence level. Using the curvature of the observed muons in the 1.3 T MINOS magnetic field ν_μ and ν̅ _μ interactions are separated. The ratio of ν̅ _μ to ν_μ events in the data is compared to the Monte Carlo expectation assuming neutrinos and antineutrinos oscillate in the same manner, giving R_{ν̅ μ/νμ}^data/R_{ν̅ μ/νμ}^MC=0.96_-0.27^+0.38(stat.)±0.15(sys.), where the errors are the statistical and systematic uncertainties. Although the statistics are limited, this is the first direct observation of atmospheric neutrino interactions separately for ν_μ and ν̅ _μ.

A general analysis of Q-ball solutions of the supersymmetric F-term hybrid inflation field equations is given. The solutions consist of a complex inflaton field and a real symmetry-breaking field, with a conserved global charge associated with the inflaton. It is shown that the Q-ball solutions for any value of the superpotential coupling, κ, may be obtained from those with κ=1 by rescaling the space coordinates. The complete range of Q-ball solutions for the case κ=1 is given, from which all possible F-term inflation Q-balls can be obtained. The possible role of F-term inflation Q-balls in cosmology is discussed.

The first hohlraum experiments on the National Ignition Facility (NIF) using the initial four laser beams tested radiation temperature limits imposed by plasma filling. For a variety of hohlraum sizes and pulse lengths, the measured x-ray flux shows signatures of filling that coincide with hard x-ray emission from plasma streaming out of the hohlraum. These observations agree with hydrodynamic simulations and with an analytical model that includes hydrodynamic and coronal radiative losses. The modeling predicts radiation temperature limits with full NIF (1.8 MJ), greater, and of longer duration than required for ignition hohlraums.

We present two- and three-dimensional simulations of the growth of quantum fluctuations of the scalar fields in supersymmetric hybrid inflation models. For a natural range of couplings, subhorizon quantum fluctuations undergo rapid growth due to scalar field dynamics, resulting in the formation of quasistable nontopological solitons (inflaton condensate lumps) which dominate the postinflation era.

We consider the conditions which must be satisfied for a Majorana RH sneutrino, a massive right-handed (RH) sneutrino associated with the seesaw mechanism of Majorana neutrino masses, to play the role of the curvaton. Planck-scale suppressed nonrenormalizable terms in the RH neutrino superpotential must be eliminated to a high-order if the RH sneutrino curvaton is to dominate the energy density before it decays, which can be achieved via an R-symmetry which is broken to R-parity by the Giudice-Maseiro mechanism. In order to evade thermalization of the curvaton condensate, one RH neutrino mass eigenstate must have small Yukawa couplings, corresponding to a lightest neutrino mass m_ν1≲10^-3  eV. A time-dependent lepton asymmetry will be induced in the RH sneutrino condensate by the Affleck-Dine mechanism driven by SUSY breaking B-terms associated with the RH neutrino masses. Requiring that the resulting baryon asymmetry and isocurvature perturbations are acceptably small imposes an upper bound on the RH neutrino mass. We show that a scenario consistent with all constraints is obtained for a RH neutrino mass in the range 10²-10⁴  GeV when the RH sneutrino decay temperature is greater than 100  GeV and lightest neutrino mass m_ν1≈10^-3  eV. Larger RH neutrino masses are possible for smaller m_ν1. The resulting scenario is generally consistent with a solution of the cosmic string problem of D-term inflation.

We consider the curvaton scenario in the context of supersymmetry (SUSY) with gravity-mediated SUSY breaking. In the case of a large initial curvaton amplitude during inflation and a negative order H² correction to the mass squared term after inflation, the curvaton will be close to the minimum of its potential at the end of inflation. In this case the curvaton amplitude fluctuations will be damped due to oscillations around the effective minimum of the curvaton potential, requiring a large expansion rate during inflation in order to account for the observed energy density perturbations, in conflict with cosmic microwave background constraints. Here we introduce a new curvaton scenario, the phase-induced curvaton scenario, in which de Sitter fluctuations of the phase of a complex SUSY curvaton field induce an amplitude fluctuation that is unsuppressed even in the presence of a negative order H² correction and large initial curvaton amplitude. This scenario is closely related to the Affleck-Dine mechanism and a curvaton asymmetry is naturally generated in conjunction with the energy density perturbations. Cosmological energy density perturbations can be explained with an expansion rate H≈10¹² GeV during inflation.

We demonstrate the existence of two-field Q-ball solutions of the scalar field equations of supersymmetric D- and F-term hybrid inflation. The solutions consist of a complex inflaton field together with a real symmetry breaking field. Such inflatonic Q-balls may play a fundamental role in reheating and the post-inflation era of supersymmetric hybrid inflation models.

It has been shown that hybrid inflation may end with the formation of non-topological solitons of the inflaton field. As a first step towards a fully realistic picture of the post-inflation era and reheating in supersymmetric hybrid inflation models, we study the classical scalar field equations of a supersymmetric hybrid inflation model using a semianalytical ansatz for the spatial dependence of the fields. Using the minimal D-term inflation model as an example, the inflaton field is evolved using the full 1-loop effective potential from the slow-rolling era to the U(1)_FI symmetry-breaking phase transition. Spatial perturbations of the inflaton corresponding to quantum fluctuations are introduced for the case where there is spatially coherent U(1)_FI symmetry breaking. The maximal growth of the dominant perturbation is found to depend only on the ratio of superpotential coupling λ to the gauge coupling g. The inflaton condensate fragments to non-topological solitons for λ/g≳0.09. The possible consequences of nontopological soliton formation in fully realistic supersymmetric hybrid inflation models are discussed.

We consider the possibility that a right-handed sneutrino can serve as the source of energy density perturbations leading to structure formation in cosmology. The cosmological evolution of a coherently oscillating condensate of right-handed sneutrinos is studied for the case where reheating after inflation is due to perturbative inflaton decays. For the case of Dirac neutrinos, it is shown that some suppression of Planck scale-suppressed corrections to the right-handed neutrino superpotential is necessary in order to have sufficiently late decay of the right-handed sneutrinos. cH² corrections to the sneutrino mass squared term must also be suppressed during inflation (|c|≲0.1), in which case, depending on the magnitude of |c| during inflation, a significantly blue (if c>0) or red (if c<0) perturbation spectrum is possible. R parity must also be broken in order to ensure that the Universe is not overclosed by the lightest supersymmetric particles from the late decay (at temperatures 1-10 MeV) of the right-handed sneutrino condensate. The resulting expansion rate during inflation can be significantly smaller than in conventional supersymmetric inflation models (as low as 10⁶ GeV is possible). For the case of Majorana neutrinos, a more severe suppression of Planck-suppressed superpotential corrections is required. In addition, the Majorana sneutrino condensate is likely to be thermalized before it can dominate the energy density, which would exclude the Majorana right-handed sneutrino as a curvaton.

Inflation ends with the formation of a Bose condensate of inflatons. We show that in hybrid inflation models this condensate is typically unstable with respect to spatial perturbations and can fragment to condensate lumps. The case of D-term inflation is considered as an example and it is shown that fragmentation occurs if λ≳0.2g, where λ is the superpotential coupling and g is the U(1)_FI gauge coupling. Condensate fragmentation can result in an effective enhancement of inflaton annihilations over decays as the main mode of reheating. In the case of D-term inflation models in which the standard model fields carry U(1)_FI charges, if condensate fragmentation occurs then reheating is dominated by inflaton annihilations, typically resulting in the overproduction of thermal gravitinos. Fragmentation may also have important consequences for SUSY flat direction dynamics and for preheating.

The NuTeV Collaboration recently reported a value of sin²θ_W measured in neutrino-nucleon scattering that is 3 standard deviations above the standard model prediction. This result is derived assuming that (1) the strange sea is quark-antiquark symmetric, s(x)=s̅ (x), and (2) up and down quark distributions are symmetric under the simultaneous interchange of u↔d and p↔n. We report the impact of violations of these symmetries on sin²θ_W and discuss the theoretical and experimental constraints on such asymmetries.

Limits on ν_μ→ν_e and ν̅ _μ→ν̅ _e oscillations are extracted using the NuTeV detector with sign-selected ν_μ and ν̅ _μ beams. In ν̅ _μ mode, for the case of sin²2α  =  1, Δm²>2.6  eV² is excluded, and for Δm²≫1000 eV², sin²2α>1.1×10^-3. The NuTeV data exclude the high Δm² end of ν̅ _μ→ν̅ _e oscillation parameters favored by the LSND experiment without the need to assume that the oscillation parameters for ν and ν̅ are the same. We present the most stringent experimental limits for ν_μ(ν̅ _μ)→ν_e(ν̅ _e) oscillations in the large Δm² region.

Internal dielectronic excitation (IDE) is a correlated atomic physics process that takes place when the deexcitation of a Rydberg electron is accompanied by the excitation of a more tightly bound electron, resulting in a doubly excited inner-shell configuration. Subsequent x-ray emission involving an electron transition to a shell that initially contained no vacancies identifies the IDE process. IDE is mediated by the electron-electron interaction in a manner similar to a time-reversed Auger transition, and can occur during the neutralization of a slow highly charged ion interacting with a solid where there are many Rydberg levels that can give rise to correlated transitions to degenerate energy states. We have investigated IDE for a wide range of projectiles and solid targets by measuring the resulting x-ray emission. The characteristic features of the x-ray spectra suggest that IDE occurs above the surface of the solid.

We present a search for charged Higgs bosons in decays of pair-produced top quarks in pp̅ collisions at sqrt[s]  =  1.8 TeV recorded by the D0 detector at the Fermilab Tevatron collider. With no evidence for signal, we exclude most regions of the ( M_H^±,tanβ) parameter space where the decay t→ H⁺b has a branching fraction >0.36 and B(H^±→τν_τ) is large.

We show that a gauge singlet scalar S, with a coupling to the Higgs doublet of the form λ_SS^†SH^†H and with the S mass entirely generated by the Higgs expectation value, has a thermally generated relic density Ω_S≈0.3 if m_S≈(2.9–10.5) (Ω_S/0.3)^1/5(h/0.7)^2/5  MeV. Remarkably, this is very similar to the range [m_S  =  (6.6–15.4)η^2/3  MeV] required in order for the self-interaction (η/4) (S^†S)² to account for self-interacting dark matter when η is not much smaller than 1. The corresponding coupling is λ_S≈(2.7×10^-10–3.6×10^-9) (Ω_S/0.3)^2/5(h/0.7)^4/5, implying that such scalars are very weakly coupled to the standard model sector.