We examine whether the annual modulation found by the DAMA dark matter experiment can be explained by Weakly Interacting Massive Particles (WIMPs), in light of new null results from other experiments. CDMS II has already ruled out most WIMP-nucleus spin-independent couplings as an explanation for DAMA data. Hence we here focus on spin-dependent (axial vector; SD) couplings of WIMPs to nuclei. We expand upon previous work by (i) considering the general case of coupling to both protons and neutrons and (ii) incorporating bounds from all existing experiments. We note the surprising fact that CMDS II places one of the strongest bounds on the WIMP-neutron cross section, and show that SD WIMP-neutron scattering alone is excluded. We also show that SD WIMP-proton scattering alone is allowed only for WIMP masses in the 5–13 GeV range. For the general case of coupling to both protons and neutrons, we find that, for WIMP masses above 13 GeV and below 5 GeV, there is no region of parameter space that is compatible with DAMA and all other experiments. In the range (5–13) GeV, we find acceptable regions of parameter space, including ones in which the WIMP-neutron coupling is comparable to the WIMP-proton coupling.

In the model of quintessino as the dark matter particle, the dark matter and dark energy are unified in one superfield, where the dynamics of the Quintessence drives the Universe acceleration and its superpartner, quintessino, makes up the dark matter of the Universe. This scenario predicts the existence of long-lived $\tilde{\tau }$ as the next lightest supersymmetric particle. In this paper we study the possibility of detecting $\tilde{\tau }$ produced by the high energy cosmic neutrinos interacting with the earth matter. By a detailed calculation we find that the event rate is one to several hundred per year at a detector with an effective area of $1{\mathrm{k}\mathrm{m}}^2$. The study in this paper can be also applied to models of gravitino or axino dark matter particles.

We have constructed models of uniformly rotating compact stars including hyperons, Bose-Einstein condensates of antikaons, and quarks. First order phase transitions from hadronic to antikaon condensed matter and then to quark matter are considered here. For the equation of state undergoing phase transitions to antikaon condensates, the third family of compact stars are found to exist in the fixed angular velocity sequences. However, the third family solution disappears when the compact stars rotate very fast. For this equation of state, the fixed baryon number supramassive sequence shows a second stable part after the unstable region but no back bending phenomenon. On the other hand, we observe that the rotation gives rise to a second maximum beyond the neutron star maximum for the equation of state involving phase transitions to both antikaon condensed and quark matter. In this case, the back bending phenomenon has been observed in the supramassive sequence as a consequence of the first order phase transition from $K^{-}$ condensed to quark matter. And the back bending segment contains stable configurations of neutron stars.

We consider the Higgs sector in an extension of the minimal supersymmetric standard model (MSSM) with extra SM singlets, involving an extra $U(1{)}^{\prime }$ gauge symmetry, in which the domain-wall problem is avoided and the effective $\mu$ parameter is decoupled from the new gauge boson $Z^{\prime }$ mass. The model involves a rich Higgs structure very different from that of the MSSM. In particular, there are large mixings between Higgs doublets and the SM singlets, significantly affecting the Higgs spectrum, production cross sections, decay modes, existing exclusion limits, and allowed parameter range. Scalars considerably lighter than the CERN LEP2 bound (114 GeV) are allowed, and the range $\tan \beta \sim 1$ is both allowed and theoretically favored. Phenomenologically, we concentrate our study on the lighter (least model-dependent, yet characteristic) Higgs particles with significant $SU(2)$-doublet components to their wave functions, for the case of no explicit $CP$ violation in the Higgs sector. We consider their spectra, including the dominant radiative corrections to their masses from the top/stop loop. We computed their production cross sections and reexamine the existing exclusion limits at LEP2. We outline the searching strategy for some representative scenarios at a future linear collider. We emphasize that gaugino, Higgsino, and singlino decay modes are indicative of extended models and have been given little attention. We present a comprehensive list of model scenarios in the Appendices.

As part of our program of lattice simulations of three-flavor QCD with improved staggered quarks, we have calculated pseudoscalar meson masses and decay constants for a range of valence quark masses and sea-quark masses on lattices with lattice spacings of about 0.125 and 0.09 fm. We fit the lattice data to forms computed with “staggered chiral perturbation theory.” Our results provide a sensitive test of the lattice simulations, and especially of the chiral behavior, including the effects of chiral logarithms. We find: $f_{\pi }=129.5\pm 0.9\pm 3.5\mathrm{M}\mathrm{e}\mathrm{V}$, $f_K=156.6\pm 1.0\pm 3.6\mathrm{M}\mathrm{e}\mathrm{V}$, and $f_K/f_{\pi }=1.210(4)(13)$, where the errors are statistical and systematic. Following a recent paper by Marciano, our value of $f_K/f_{\pi }$ implies $|V_{us}|=0.2219(26)$. Further, we obtain $m_u/m_d=0.43(0)(1)(8)$, where the errors are from statistics, simulation systematics, and electromagnetic effects, respectively. The partially quenched data can also be used to determine several of the constants of the low energy chiral effective Lagrangian: In particular, we find $2L_8-L_5=-0.2(1)(2)\times {10}^{-3}$ at chiral scale $m_{\eta }$, where the errors are statistical and systematic. This provides an alternative (though not independent) way of estimating $m_u$; the value of $2L_8-L_5$ is far outside the range that would allow the up quark to be massless. Results for $m_s^{\overline{\mathrm{M}\mathrm{S}}}$, ${\widehat{m}}^{\overline{\mathrm{M}\mathrm{S}}}$, and $m_s/\widehat{m}$ can be obtained from the same lattice data and chiral fits, and have been presented previously in joint work with the HPQCD and UKQCD collaborations. Using the perturbative mass renormalization reported in that work, we obtain $m_u^{\overline{\mathrm{M}\mathrm{S}}}=1.7(0)(1)(2)(2)\mathrm{M}\mathrm{e}\mathrm{V}$ and $m_d^{\overline{\mathrm{M}\mathrm{S}}}=3.9(0)(1)(4)(2)\mathrm{M}\mathrm{e}\mathrm{V}$ at scale 2 GeV, with errors from statistics, simulation, perturbation theory, and electromagnetic effects, respectively.

The branching fraction of the ${\psi }^{\prime \prime }$ decays into charmless final states is estimated in the $S$- and $D$-wave charmonia mixing scheme. With the information of the hadronic decays of $J/\psi$ and ${\psi }^{\prime }$, it is found that a large branching fraction, up to 13% of the total ${\psi }^{\prime \prime }$ decays, may go to charmless final states. The experimental search for these decays is also discussed.

The shift of the $p$-wave $D_s$ meson mass due to coupling to the $DK$ channel is calculated using a QCD string model and the chiral Lagrangian. As a result the original $Q\overline{q}$ mass, 2.490 MeV, generically calculated in the relativistic quark models is shifted down to the experimental value 2317 MeV. With the same Lagrangian the shift of the radial excited $1^{-}$ level is much smaller, while the total width $\Gamma >100\mathrm{M}\mathrm{e}\mathrm{V}$ and the width ratio is in contradiction with the $D^{*}(2632)$ state observed by SELEX Collaboration.

Normally, standard (ungauged) skyrmion masses are proportional to the coupling of the Skyrme term needed for stability, and so can grow to infinite magnitude with increasing coupling. In striking contrast, when skyrmions are gauged, their masses are bounded above for any Skyrme coupling, and, instead, are of the order of monopole masses, $O(v/g)$, so that the coupling of the Skyrme term is not very important. This boundedness phenomenon and its implications are investigated.

We apply techniques recently introduced in quantum cosmology to the Schwarzschild metric inside the horizon and near the black hole singularity at $r=0$. In particular, we use the quantization introduced by Husain and Winkler, which is suggested by Loop Quantum Gravity and is based on an alternative to the Schrödinger representation introduced by Halvorson. Using this quantization procedure, we show that the black hole singularity disappears and spacetime can be dynamically extended beyond the classical singularity.

We present a new approximation method for solving the equations of motion for cosmological tensor perturbations in a Randall-Sundrum brane-world model of the type with one brane in a five-dimensional anti-de Sitter spacetime. This method avoids the problem of coordinate singularities inherent in some methods. At leading-order, the zero-mode solution replicates the evolution of perturbations in a four-dimensional Friedmann-Robertson-Walker universe in the absence of any tensor component to the matter perturbation on the brane. At next order, there is a mode-mixing effect, although, importantly, the zero-mode does not source any other modes.

The lattice formulation of quantum gravity provides a natural framework in which nonperturbative properties of the ground state can be studied in detail. In this paper we investigate how the lattice results relate to the continuum semiclassical expansion about smooth manifolds. As an example we give an explicit form for the lattice ground-state wave functional for semiclassical geometries. We then do a detailed comparison between the more recent predictions from the lattice regularized theory and results obtained in the continuum for the nontrivial ultraviolet fixed point of quantum gravity found using weak field and nonperturbative methods. In particular we focus on the derivative of the beta function at the fixed point and the related universal critical exponent $\nu$ for gravitation. Based on recently available lattice and continuum results we assess the evidence for the presence of a massless spin-two particle in the continuum limit of the strongly coupled lattice theory. Finally we compare the lattice prediction for the vacuum-polarization induced weak scale dependence of the gravitational coupling with recent calculations in the continuum, finding similar effects.

We explore the CP violation in the charged Higgs production associated with a top quark at the LHC in the minimal supersymmetric standard model. The supersymmetric phases of gaugino masses and trilinear $A$ terms lead to a CP violation of the cross section in the $pp\to gb\to t{H}^{\pm }$ process through loop corrections to the $tb{H}^{\pm }$ vertex. We find that more than 10% of CP violating asymmetry is possible when the charged Higgs boson is heavy enough.

The thermodynamics of the $\mathrm{O}(N)$ linear and nonlinear sigma models in $3+1$ dimensions is studied. We calculate the pressure to next-to-leading order in the $1/N$ expansion and show that at this order, temperature-independent renormalization is only possible at the minimum of the effective potential. The $1/N$ expansion is found to be a good expansion for $N$ as low as 4, which is the case relevant for low-energy QCD phenomenology. We consider the cases with and without explicit symmetry breaking. We show that previous next-to-leading-order calculations of the pressure are either breaking down at the temperatures of interest, or based on unjustifiable high-energy approximations.

We study $CP$ sensitive observables in chargino production in electron-positron collisions with subsequent two-body decay of one chargino into a $W$ boson. We identify the $CP$ odd elements of the $W$ boson density matrix and propose $CP$ sensitive triple-product asymmetries of the chargino decay products. We calculate the density-matrix elements, the $CP$ asymmetries, and the cross sections in the minimal supersymmetric standard model with complex parameters $\mu$ and $M_1$ for an $e^{+}{e}^{-}$ linear collider with $\sqrt{s}=800\mathrm{G}\mathrm{e}\mathrm{V}$ and longitudinally polarized beams. The asymmetries can reach $7\%$ and we discuss the feasibility of measuring these asymmetries.

We study new physics effects on the couplings of weak gauge bosons with the lightest CP-even Higgs boson ($h$), $hZZ$, and the trilinear coupling of the lightest Higgs boson, $hhh$, at the one-loop order, as predicted by the two Higgs doublet model. Those renormalized coupling constants can deviate from the standard model (SM) predictions due to two distinct origins: the tree level mixing effect of Higgs bosons and the quantum effect of additional particles in loop diagrams. The latter can be enhanced in the renormalized $hhh$ coupling constant when the additional particles show the nondecoupling property. Therefore, even in the case where the $hZZ$ coupling is close to the SM value, deviation in the $hhh$ coupling from the SM value can become as large as plus 100%, while that in the $hZZ$ coupling is at most minus 1% level. Such large quantum effect on the Higgs trilinear coupling is distinguishable from the tree level mixing effect, and is expected to be detectable at a future linear collider.

I present an analysis of fully differential single-top-quark production plus jets at next-to-leading-order. I describe the effects of jet definitions, top-quark mass, and higher orders on the shapes and normalizations of the kinematic distributions, and quantify all theoretical uncertainties. I explain how to interpret next-to-leading-order jet calculations, and compare them to showering event generators. Using the program ZTOP, I show that HERWIG and PYTHIA significantly underestimate both $s$-channel and $t$-channel single-top-quark production, and propose a scheme to match the relevant samples to the next-to-leading-order predictions.

There is a good deal of current interest in the condensate $⟨g^2{A}_{\mu }^a{A}_a^{\mu }⟩$ which has recently be shown to be the Landau gauge version of a more general gauge-invariant expression. In the present work we consider quark propagation in the presence of such a condensate which we assume to be present in the vacuum. We describe the vacuum as a random medium of gluon fields. We discuss quark propagation in that medium and show that the quark propagator has no on-mass-shell pole indicating that a quark cannot propagate over extended distances. That is, the quark is a nonpropagating mode in the gluon condensate.

The merging procedure of tree-level matrix elements and the subsequent parton shower as implemented in the new event generator SHERPA will be validated for the example of $W/Z+\mathrm{j}\mathrm{e}\mathrm{t}\mathrm{s}$ production at the Tevatron. Comparisons with results obtained from other approaches and programs and with experimental results clearly show that the merging procedure yields relevant and correct results at both the hadron and parton levels.

QCD plasma instabilities appear to play an important role in the equilibration of quark-gluon plasmas in heavy-ion collisions in the theoretical limit of weak coupling (i.e. asymptotically high energy). It is important to understand what nonlinear physics eventually stops the exponential growth of unstable modes. It is already known that the initial growth of plasma instabilities in QCD closely parallels that in QED. However, once the unstable modes of the gauge fields grow large enough for non-Abelian interactions between them to become important, one might guess that the dynamics of QCD plasma instabilities and QED plasma instabilities become very different. In this paper, we give suggestive arguments that non-Abelian self-interactions between the unstable modes are ineffective at stopping instability growth, and that the growing non-Abelian gauge fields become approximately Abelian after a certain stage in their growth. This in turn suggests that understanding the development of QCD plasma instabilities in the nonlinear regime may have close parallels to similar processes in traditional plasma physics. We conjecture that the physics of collisionless plasma instabilities in SU(2) and SU(3) gauge theory becomes equivalent, respectively, to (i) traditional plasma physics, which is U(1) gauge theory, and (ii) plasma physics of U(1)$\times$U(1) gauge theory.

We show in a model independent way the equality of the branching fractions and strong phases for $\overline{B}\to D_{1}M$ and $\overline{B}\to D_2^{*}M$ at leading order in ${\Lambda }_{\mathrm{Q}\mathrm{C}\mathrm{D}}/Q$ and ${\alpha }_s(Q)$ where $Q=\{m_b,m_c,E_M\}$ and $M$ is a light meson. These results apply in the color allowed and color suppressed channels and follow from a factorization theorem in soft-collinear effective theory combined with heavy quark symmetry. The expected heavy quark symmetry suppression of leading order contributions in the color allowed sector based on analysis of semileptonic decays is shown to disappear at maximum recoil. Subleading corrections are suppressed by at least one power of ${\Lambda }_{\mathrm{Q}\mathrm{C}\mathrm{D}}/Q$ and this is explicitly verified for subleading semileptonic form factors at maximum recoil.