The ${\Lambda }_c^{+}$ baryon mass is measured using ${\Lambda }_c^{+}\to \Lambda K_S^0{K}^{+}$ and ${\Lambda }_c^{+}\to {\Sigma }^0{K}_S^0{K}^{+}$ decays reconstructed in $232{\mathrm{fb}}^{-1}$ of data collected with the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ storage ring. The ${\Lambda }_c^{+}$ mass is measured to be $2286.46\pm 0.14\mathrm{MeV}/c^2$. The dominant systematic uncertainties arise from the amount of material in the tracking volume and from the magnetic field strength.

We analyze the reorganization of free field theory correlators to closed string amplitudes investigated in previous papers in the case of Euclidean thermal field theory and study how the dual bulk geometry is encoded on them. The expectation value of Polyakov loop, which is an order parameter for confinement-deconfinement transition, is directly reflected on the dual bulk geometry. The dual geometry of the confined phase is found to be AdS space periodically identified in Euclidean time direction. The gluing of Schwinger parameters, which is a key step for the reorganization of field theory correlators, works in the same way as in the nonthermal case. In the deconfined phase the gluing is made possible only by taking the dual geometry correctly. The dual geometry for the deconfined phase does not have a noncontractable circle in the Euclidean time direction.

We investigate the theory of the bosonic-fermionic noncommutativity, $[x^{\mu },{\theta }^{\alpha }]=i{\lambda }^{\mu \alpha }$, and the Wess-Zumino model deformed by the noncommutativity. Such noncommutativity links well-known space-time noncommutativity to superspace non-anticommutativity. The deformation has the nilpotency. We can explicitly evaluate noncommutative effect in terms of new interactions between component fields. The interaction terms that have Grassmann couplings are induced. The noncommutativity does completely break full $\mathcal{N}=1$ supersymmetry to $\mathcal{N}=0$ theory in Minkowski signature. Similar to the space-time noncommutativity, this theory has higher derivative terms and becomes nonlocal theory. However this nonlocality is milder than the space-time noncommutative field theory. Because of the nilpotent feature of the coupling constants, we find that there are only finite number of Feynman diagrams that give noncommutative corrections at each loop order.

Extending the analysis of C. de Rham and S. Webster [Phys. Rev. D 71, 124025 (2005)], we obtain a formal expression for the coupling between brane matter and the radion in a Randall-Sundrum braneworld. This effective theory is correct to all orders in derivatives of the radion in the limit of small brane separation, and, in particular, contains no higher than second derivatives. In the case of cosmological symmetry the theory can be obtained in closed form and reproduces the five-dimensional behavior. Perturbations in the tensor and scalar sectors are then studied. When the branes are moving, the effective Newtonian constant on the brane is shown to depend both on the distance between the branes and on their velocity. In the small-distance limit, we compute the exact dependence between the four-dimensional and the five-dimensional Newtonian constants.

We calculate the radiative corrections to the angular correlation ${\widehat{\mathbf{s}}}_1·\widehat{\mathbf{l}}$ to order $(\alpha /\pi )(q/M_1)$. The final results are presented with the triple integration of the bremsstrahlung photon to be performed numerically and in an analytical form. The results are useful in the analysis of precision experiments involving light and heavy quarks. It is assumed that the real photons are kinematically discriminated. Our results are model-independent.

We employ a 3 flavor Nambu–Jona-Lasinio (NJL) model to stress some general remarks about the QCD critical line. The dependence of the critical curve on ${\mu }_q=({\mu }_u+{\mu }_d)/2$ and ${\mu }_I=({\mu }_u-{\mu }_d)/2$ is discussed. The quark masses are varied to confirm that, in agreement with universality arguments, the order of transition depends on the number of active flavors $N_f$. The slope of the critical curve vs chemical potential is studied as a function of $N_f$. We compare our results with those recently obtained in lattice simulations to establish a comparison among different models.

Behavior of static axially-symmetric monopole-antimonopole and vortex ring solutions of the SU(2) Yang-Mills-Higgs theory in an external uniform magnetic field is considered. It is argued that the axially-symmetric monopole-antimonopole chains and vortex rings can be treated as a bounded electromagnetic system of the magnetic charges and the electric current rings. The magnitude of the external field is a parameter which may be used to test the structure of the static potential of the effective electromagnetic interaction between the monopoles with opposite orientation in the group space. It is shown that for non-Bogomol’nyi-Prasad-Sommerfield (BPS) solutions there is a local minimum of this potential.

We introduce the idea of bosonic seesaw mechanism in analogy with the seesaw mechanism. Bosonic seesaw is a new symmetry breaking mechanism, and we apply it to explain electroweak symmetry breaking as an inevitable consequence of supersymmetry breaking. The breaking of electroweak symmetry occurs at tree level once supersymmetry is broken. Absence of color/charge breaking in this model is related to doublet-triplet splitting in the grand unified theory. An extension of the minimal supersymmetric standard model with a weak triplet shows very interesting results, especially when $\mu =0$. It provides natural understanding of why we have only electroweak symmetry breaking rather than having color/charge breaking. In the limit $\mu =0$, the model predicts very light chargino mass, 104 GeV, while Higgs is heavy, 130 GeV.

We consider Drell-Yan process in the threshold region $z\to 1$ where large logarithms appear due to soft-gluon radiations. We present a soft-collinear effective theory approach to resum these Sudakov-type logarithms following an earlier treatment of deep-inelastic scattering, and the result is consistent with that obtained through a standard perturbative QCD factorization.

We study the charmless rare decays $B\to K^{*}{K}^{*}$ within the perturbative QCD picture. We calculate not only factorizable and nonfactorizable diagrams, but also annihilation ones. Our predictions are the following: The longitudinal polarization fraction vary from 75% to 99% depending on channels, the branching ratios are of order ${10}^{-7}$ for $B^0({\overline{B}}^0)\to K^{*0}{\overline{K}}^{*0}$ and $B^{\pm }\to K^{*\pm }{\overline{K}}^{*0}(K^{*0})$, much bigger than that for $B^0({\overline{B}}^0)\to K^{*+}{K}^{*-}$(${10}^{-8}$). The direct $\mathrm{CP}$ asymmetry in $B^{\pm }\to K^{*\pm }{\overline{K}}^{*0}(K^{*0})$ and $B^0({\overline{B}}^0)\to K^{*+}{K}^{*-}$ is about $-15\%$ and $-65\%$ if we choose $\alpha ({\phi }_2)$ as $95°$. The direct $\mathrm{CP}$ violation in $B^0({\overline{B}}^0)\to K^{*0}{\overline{K}}^{*0}$ decays is negligible if there is not strong final state interactions. Our predictions will be tested in the future $B$ experiments.

We discuss in detail the photon spectrum of radiative ${\rm Y}(1S)$ decays taking into account a number of results that have recently appeared in the literature. In particular, we show how to consistently combine expressions which are valid in the upper end point region, where NRQCD factorization breaks down, with those of the central region, where NRQCD factorization holds. An excellent description of data is achieved, but theoretical errors are large.

The presence of a tau component in the flux of atmospheric neutrinos inside the Earth, due to flavor oscillations, makes these neutrinos a valuable probe of interactions of the tau neutrino with matter. We study—analytically and numerically—the effects of nonstandard interactions in the ${\nu }_e-{\nu }_{\tau }$ sector on atmospheric neutrino oscillations, and calculate the bounds on the exotic couplings that follow from combining the atmospheric neutrino and K2K data. We find very good agreement between numerical results and analytical predictions derived from the underlying oscillation physics. While improving on existing accelerator bounds, our bounds still allow couplings of the size comparable to the standard weak interaction. The inclusion of new interactions expands the allowed region of the vacuum oscillation parameters towards smaller mixing angles, $0.2\lesssim {sin}^2{\theta }_{23}\lesssim 0.7$, and slightly larger mass squared splitting, $1.5\times {10}^{-3}\mathrm{e}{\mathrm{V}}^2\lesssim |\Delta m_{23}^2|\lesssim 4.0\times {10}^{-3}\mathrm{e}{\mathrm{V}}^2$, compared to the standard case. The impact of the K2K data on all these results is significant; further important tests of the ${\nu }_e-{\nu }_{\tau }$ exotic couplings will come from neutrino beam experiments such as MINOS and long baseline projects.

We use the Wilkinson Microwave Anisotropy Probe (WMAP) data on the spectrum of cosmic microwave background anisotropies to put constraints on the present amount of lepton asymmetry $L$, parametrized by the dimensionless chemical potential (also called degeneracy parameter) $\xi$ and on the effective number of relativistic particle species. We assume a flat cosmological model with three thermally distributed neutrino species having all the same mass and chemical potential, plus an additional amount of effectively massless exotic particle species. The extra energy density associated to these species is parametrized through an effective number of additional species $\Delta N_{\mathrm{others}}^{\mathrm{eff}}$. We find that $0<|\xi |<1.1$ and correspondingly $0<|L|<0.9$ at $2\sigma$, so that WMAP data alone cannot firmly rule out scenarios with a large lepton number; moreover, a small preference for this kind of scenarios is actually found. We also discuss the effect of the asymmetry on the estimation of other parameters and, in particular, of the neutrino mass. In the case of perfect lepton symmetry, we obtain the standard results. When the amount of asymmetry is left free, we find $\sum _{}^{}{m}_{\nu }<3.6\mathrm{eV}$ at $2\sigma$. Finally we study how the determination of $|L|$ is affected by the assumptions on $\Delta N_{\mathrm{others}}^{\mathrm{eff}}$. We find that lower values of the extra energy density allow for larger values of the lepton asymmetry, effectively ruling out, at $2\sigma$ level, lepton symmetric models with $\Delta N_{\mathrm{others}}^{\mathrm{eff}}\simeq 0$.

We discuss the links between generalized parton distributions (GPDs) and elastic nucleon form factors. These links, in the form of sum rules, represent powerful constraints on parametrizations of GPDs. A Regge parametrization for GPDs at small momentum transfer, is extended to the large momentum transfer region and it is found to describe the basic features of proton and neutron electromagnetic form factor data. This parametrization is used to estimate the quark contribution to the nucleon spin.

In previous work, we have shown that large $N$ field theory amplitudes, in Schwinger parametrized form, can be organized into integrals over the stringy moduli space ${\mathcal{M}}_{g,n}\times R_{+}^n$. Here we flesh this out into a concrete implementation of open-closed string duality. In particular, we propose that the closed string world sheet is reconstructed from the unique Strebel quadratic differential that can be associated to (the dual of) a field theory skeleton graph. We are led, in the process, to identify the inverse Schwinger proper times (${\sigma }_i=1/{\tau }_i$) with the lengths of edges of the critical graph of the Strebel differential. Kontsevich’s matrix model derivation of the intersection numbers in moduli space provides a concrete example of this identification. It also exhibits how closed string correlators emerge very naturally from the Schwinger parameter integrals. Finally, to illustrate the utility of our approach to open-closed string duality, we outline a method by which a world sheet operator product expansion can be directly extracted from the field theory expressions. Limits of the Strebel differential for the four punctured sphere play a key role.

We estimate the reaction mechanisms for the photoproduction of the ${\Theta }^{+}(1540)$ resonance on the nucleon, through $K$ and $K^{*}$ Regge exchanges. We compare the size of the cross sections for the $\gamma n\to K^{-}{\Theta }^{+}$ and $\gamma p\to {\overline{K}}^0{\Theta }^{+}$ reactions and investigate their sensitivity to the spin-parity assignments $J^P={\frac{1}{2}}^{\pm },{\frac{3}{2}}^{\pm }$ for the ${\Theta }^{+}$ resonance. The model allows one to estimate the cross sections corresponding with a given upper bound on the width of the ${\Theta }^{+}$. Within this model, the cross sections on the neutron are found to be around a factor of 5 larger than the ones on the proton, due to the presence of charged $K$ exchange for the reaction on a neutron target. Furthermore, the photon asymmetry is found to display a pronounced sensitivity to the parity of the ${\Theta }^{+}$, making it a very promising observable to help determine the quantum numbers of the ${\Theta }^{+}$ resonance.

We report on a search for ${\Lambda }_b^0\to p{\pi }^{-}$ and ${\Lambda }_b^0\to p{K}^{-}$ (and charge conjugate) decays in $p\overline{p}$ collisions at $\sqrt{s}=1.96\mathrm{TeV}$ using $193\mathrm{p}{\mathrm{b}}^{-1}$ of data collected by the CDF II experiment at the Fermilab Tevatron Collider. Data were collected using a track trigger that has been optimized to select tracks belonging to a secondary vertex that is typical of two-body charmless decays of $b$-flavored hadrons, including ${\Lambda }_b^0$ baryons. As no ${\Lambda }_b^0$ signal was observed, we set the upper limits on the branching fraction $\mathcal{B}({\Lambda }_b^0\to p{h}^{-})$, where $h$ is $K$ or $\pi$, of $2.3\times {10}^{-5}$ at 90% C.L. and $2.9\times {10}^{-5}$ at 95% C.L.

We study the connection of the chiral dynamics in QED and QCD in a strong magnetic field with noncommutative field theories (NCFT). It is shown that these dynamics determine complicated nonlocal NCFT. In particular, although the interaction vertices for electrically neutral composites in these gauge models can be represented in the space with noncommutative spatial coordinates, there is no field transformation that could put the vertices in the conventional form considered in the literature. It is unlike the Nambu-Jona-Lasinio (NJL) model in a magnetic field where such a field transformation can be found, with a cost of introducing an exponentially damping form factor in field propagators. The crucial distinction between these two types of models is in the characters of their interactions, being short-range in the NJL-like models and long-range in gauge theories. The relevance of the NCFT connected with the gauge models for the description of the quantum Hall effect in condensed matter systems with long-range interactions is briefly discussed.