The topcolor-assisted technicolor (TC2) model predicts the existence of the charged top-pions (${\pi }_t^{\pm }$), whose large couplings with the third generation fermions will induce the charged top-pion production associated with the bottom and antibottom quark pair at the CERN Large Hadron Collider (LHC) through the parton processes $c\overline{b}\to {\pi }_t^{+}b\overline{b}$ and $u\overline{d}(c\overline{s})\to {\pi }_t^{+}b\overline{b}$. In this report, we examine these productions and find that, due to the small standard model backgrounds, their production rates can exceed the $3\sigma$ sensitivity of the LHC in a large part of parameter space, so these processes may serve as a good probe of the TC2 model.

Since the $N^{*}(1535)$ resonance was found to have large coupling to the strangeness due to its possible large $s\overline{s}$ component, we investigate the possible contribution of the $t$-channel $N^{*}(1535)$ exchange for the $p\overline{p}\to \varphi \varphi$ reaction. Our calculation indicates that the new mechanism may give significant contribution for the energies above 2.25 GeV and may be an important source for evading the Okubo-Zweig-Iizuka rule in the $\varphi$ production from $N\overline{N}$ annihilation.

We study the low transverse momentum ($p_T$) distribution of the $Z$-boson at hadron colliders for $p_T\sim {\Lambda }_{\mathrm{QCD}}$ using a factorization and resummation formula derived in the soft-collinear effective theory (SCET). In the region $p_T\sim {\Lambda }_{\mathrm{QCD}}$, new nonperturbative effects arise that cannot be entirely captured by the standard parton distribution functions, and require an additional new nonperturbative transverse momentum function (TMF). The TMF is field-theoretically defined in SCET, fully gauge-invariant, and captures the nonperturbative dynamics that affect the $p_T$-distribution in the region $p_T\sim {\Lambda }_{\mathrm{QCD}}$. The TMF also reduces to the expected perturbative result in the region $p_T\gg {\Lambda }_{\mathrm{QCD}}$. We develop phenomenological models for these TMFs in the nonperturbative region, and discuss in detail fits to Tevatron data in which both experimental and theoretical errors are carefully treated.

A sequential fourth generation is still viable, but the $t^{\prime }$ and $b^{\prime }$ quarks are constrained not to be too far apart in mass. The $t^{\prime }\to bW$ and $b^{\prime }\to tW$ decay channels are still being pursued at the Tevatron, which will soon be surpassed by the LHC. We use a convolution method with up to five-body final states to study $t^{\prime }$ and $b^{\prime }$ decays. We show how the two decay branches for $m_{b^{\prime }}$ below the $tW$ threshold, $b^{\prime }\to t{W}^{*}$ and $t^{*}W$, merge with $b^{\prime }\to tW$ above the threshold. We then consider the heavy-to-heavy transitions $b^{\prime }\to t^{\prime (*)}{W}^{(*)}$ (or $t^{\prime }\to b^{\prime (*)}{W}^{(*)}$), as they are not suppressed by quark mixing. We find that, because of the threshold sensitivity of the branching fraction of $t^{\prime }\to b^{\prime }{W}^{*}$ (or $b^{\prime }\to t^{\prime }{W}^{*}$), it is possible to measure the strength of the CKM mixing element $V_{t^{\prime }b}$ (or $V_{t{b}^{\prime }}$), especially when it is rather small. We urge experimenters to pursue and separate the $t^{\prime }\to b^{\prime }{W}^{*}$ (or $b^{\prime }\to t^{\prime }{W}^{*}$) decay in their search programs.

Dark matter pair production at high energy colliders may leave observable signatures in the energy and momentum spectra of the objects recoiling against the dark matter. We use LEP data on monophoton events with large missing energy to constrain the coupling of dark matter to electrons. Within a large class of models, our limits are complementary to and competitive with limits on dark matter annihilation and on WIMP-nucleon scattering from indirect and direct searches. Our limits, however, do not suffer from systematic and astrophysical uncertainties associated with direct and indirect limits. For example, we are able to rule out light ($\lesssim 10\mathrm{GeV}$) thermal relic dark matter with universal couplings exclusively to charged leptons. In addition, for dark matter mass below about 80 GeV, LEP limits are stronger than Fermi constraints on annihilation into charged leptons in dwarf spheroidal galaxies. Within its kinematic reach, LEP also provides the strongest constraints on the spin-dependent direct detection cross section in models with universal couplings to both quarks and leptons. In such models the strongest limit is also set on spin-independent scattering for dark matter masses below $\sim 4\mathrm{GeV}$. Throughout our discussion, we consider both low energy effective theories of dark matter, as well as several motivated renormalizable scenarios involving light mediators.

We consider the problem of neutrino masses and mixing within the framework of a nonminimal supersymmetric $SU(5)$ model extended by adding a set of $\underline{\mathbf{1}}$, $\underline{\mathbf{24}}$ chiral superfields accommodating three right-handed neutrinos. A type $\mathrm{I}+\mathrm{III}$ seesaw mechanism can then be realized, giving rise to a hierarchical mass spectrum for the light neutrinos of the form $m_3>m_2\gg m_1$, consistent with present data. The extra colored states are pushed to the unification scale by proton stability constraints, while the intermediate seesaw energy scale and the unification scale are maintained in phenomenologically acceptable ranges. We also examine the issue of the large neutrino mixing hierarchy ${\theta }_{23}>{\theta }_{12}\gg {\theta }_{13}$ in the above framework of hierarchical neutrino masses.

We calculate the energy release associated with first-order phase transition between different types of single-flavor color superconductivity in a magnetic field.

We study the properties of the leading Regge trajectory in open string theory including the open string planar one-loop corrections. With $SU(N)$ Chan-Paton factors, the sum over planar open string multiloop diagrams describes the ’t Hooft limit $N\to \infty$ with $N{g}_s^2$ fixed. Our motivation is to improve the understanding of open string theory at finite ${\alpha }^{\prime }$ as a model of gauge field theories. $SU(N)$ gauge theories in $D$ space-time dimensions are described by requiring open strings to end on a stack of $N$ $\mathrm{D}p$-branes of space-time dimension $D=p+1$. The large $N$ leading trajectory $\alpha (t)=1+{\alpha }^{\prime }t+\Sigma (t)$ can be extracted, through order $g^2$, from the $s\to -\infty$ limit, at fixed $t$, of the four open string tree and planar loop diagrams. We analyze the $t\to 0$ behavior with the result that $\Sigma (t)\sim -C{g}^2(-{\alpha }^{\prime }t{)}^{(D-4)/2}/(D-4)$. This result precisely tracks the 1-loop Reggeized gluon of gauge theory in $D>4$ space-time dimensions. In particular, for $D\to 4$ it reproduces the known infrared divergences of gauge theory in 4  dimensions with a Regge trajectory behaving as $-\ln (-{\alpha }^{\prime }t)$. We also study $\Sigma (t)$ in the limit $t\to -\infty$ and show that, when $D<8$, it behaves as ${\alpha }^{\prime }t/(\ln (-{\alpha }^{\prime }t){)}^{\gamma }$, where $\gamma >0$ depends on $D$ and the number of massless scalars. Thus, as long as $4<D<8$, the 1-loop correction stays small relative to the tree trajectory for $-{\alpha }^{\prime }t$ arbitrarily large. Finally we present the results of numerical calculations of $\Sigma (t)$ for all negative $t$.

We study the field theoretical description of a generic theory of gravity flowing to Einstein general relativity in IR. We prove that, if ghost-free, in the weakly-coupled regime such a theory can never become weaker than general relativity. Using this fact, as a by-product, we suggest that in a ghost-free theory of gravity trans-Planckian propagating quantum degrees of freedom cannot exist. The only physical meaning of a trans-Planckian pole is the one of a classical state (black hole) which is described by the light IR quantum degrees of freedom and gives exponentially-suppressed contributions to virtual processes. In this picture Einstein gravity is UV self-complete, although not Wilsonian, and sub-Planckian distances are unobservable in any healthy theory of gravity. We then finally show that this UV/IR correspondence puts a severe constraint on any attempt of conventional Wilsonian UV-completion of trans-Planckian gravity. Specifically, there is no well-defined energy domain in which gravity could become asymptotically weak or safe.

Cosmic rays are hampered by the Moon and a deficit in its direction is expected (the so-called Moon shadow). The Moon shadow is an important tool to determine the performance of an air shower array. Indeed, the westward displacement of the shadow center, due to the bending effect of the geomagnetic field on the propagation of cosmic rays, allows the setting of the absolute rigidity scale of the primary particles inducing the showers recorded by the detector. In addition, the shape of the shadow permits to determine the detector point spread function, while the position of the deficit at high energies allows the evaluation of its absolute pointing accuracy. In this paper we present the observation of the cosmic ray Moon shadowing effect carried out by the ARGO-YBJ experiment in the multi-TeV energy region with high statistical significance (55 standard deviations). By means of an accurate Monte Carlo simulation of the cosmic rays propagation in the Earth-Moon system, we have studied separately the effect of the geomagnetic field and of the detector point spread function on the observed shadow. The angular resolution as a function of the particle multiplicity and the pointing accuracy have been obtained. The primary energy of detected showers has been estimated by measuring the westward displacement as a function of the particle multiplicity, thus calibrating the relation between shower size and cosmic ray energy. The stability of the detector on a monthly basis has been checked by monitoring the position and the deficit of the Moon shadow. Finally, we have studied with high statistical accuracy the shadowing effect in the day/”night” time looking for possible effect induced by the solar wind.

We study the effect of final state radiation in the process $e^{+}+e^{-}\to \overline{p}+p(\gamma )$, in the kinematical conditions of the BABAR and BESIII experiments. We show that this effect has a large dependence on the kinematical conditions, in particular, in the low $x$ region ($x$ is fraction of the incident energy carried by the radiated photon) and should be taken into account in the analysis of precise experiments.

We discuss and propose the minimal generalization of the Witten-Veneziano relation to finite temperatures, prompted by STAR and PHENIX experimental results on the multiplicity of ${\eta }^{\prime }$ mesons. After explaining why these results show that the zero-temperature Witten-Veneziano relation cannot be straightforwardly extended to temperatures $T$ too close to the chiral restoration temperature $T_{\mathrm{Ch}}$ and beyond, we find the quantity which should replace, at $T>0$, the Yang-Mills topological susceptibility appearing in the $T=0$ Witten-Veneziano relation, in order to avoid the conflict with experiment at $T>0$. This is illustrated through concrete $T$-dependences of pseudoscalar meson masses in a chirally well-behaved, Dyson-Schwinger approach, but our results and conclusions are of a more general nature and, essentially, model-independent.

We consider the pseudocritical temperatures for the chiral and deconfinement transitions within a Polyakov-loop Dyson-Schwinger equation approach which employs a nonlocal rank-2 separable model for the effective gluon propagator. These pseudocritical temperatures differ by a factor of 2 when the quark and gluon sectors are considered separately, but get synchronized and become coincident when their coupling is switched on. The coupling of the Polyakov loop to the chiral quark dynamics narrows the temperature region of the QCD transition in which chiral symmetry and deconfinement is established. We investigate the effect of rescaling the parameter $T_0$ in the Polyakov-loop potential on the QCD transition for both the logarithmic and polynomial forms of the potential. While the critical temperatures vary in a similar way, the width of the transition is more strongly affected for the logarithmic potential. For this potential, the character of the transition changes from crossover to a first-order one when $T_0<210\mathrm{MeV}$, but it remains crossover in the whole range of relevant $T_0$ values for the polynomial form.

Supersymmetric (SUSY) grand unified theories based on exceptional gauge groups such as $E_6$ have recently triggered a lot of interest. Aside from top-down motivations, they contain phenomenologically interesting states with leptoquark quantum numbers. Their SUSY partners, leptoquarkinos, will appear similar to all $R$-odd particles in decay cascades, but mass edges in kinematic distributions—originating from the same semiexclusive final states—will however have major differences to the corresponding edges of ordinary squarks. This distortion of standard observables bears the opportunity to detect them at the LHC, but may also pose significant confusion of underlying model assumptions, which should be handled with care and, if interpreted falsely, might even prevent a possible discovery.

It is argued that the adjoint torelon loop, i.e., a Polyakov loop in the adjoint representation running in a spatial, rather than temporal, direction, is an observable which is sensitive to the presence of long color electric flux tubes at high temperatures. We show via lattice Monte Carlo simulations that this observable has a sharp peak at the deconfinement transition, remains much larger than the vacuum value for some range of $T>T_c$, and falls below the vacuum value for $T>2T_c$. This result suggests that long electric flux tubes may persist for a finite range of temperatures past the deconfinement transition and, at some stage, disappear, presumably melting into a plasma of gluons. As a side remark, we point out that our results at $T<T_c$ imply that the eigenvalues of ordinary Polyakov loop holonomies in the confinement phase have a slight tendency to attract rather than repel, which may be relevant to certain models of confinement.

We report on the event structure and double helicity asymmetry ($A_{LL}$) of jet production in longitudinally polarized $p+p$ collisions at $\sqrt{s}=200\mathrm{GeV}$. Photons and charged particles were measured by the PHENIX experiment at midrapidity $|\eta |<0.35$ with the requirement of a high-momentum ($>2\mathrm{GeV}/c$) photon in the event. Event structure, such as multiplicity, $p_T$ density and thrust in the PHENIX acceptance, were measured and compared with the results from the pythia event generator and the geant detector simulation. The shape of jets and the underlying event were well reproduced at this collision energy. For the measurement of jet $A_{LL}$, photons and charged particles were clustered with a seed-cone algorithm to obtain the cluster $p_T$ sum ($p_T^{\mathrm{reco}}$). The effect of detector response and the underlying events on $p_T^{\mathrm{reco}}$ was evaluated with the simulation. The production rate of reconstructed jets is satisfactorily reproduced with the next-to-leading-order and perturbative quantum chromodynamics jet production cross section. For $4<p_T^{\mathrm{reco}}<12\mathrm{GeV}/c$ with an average beam polarization of $⟨P⟩=49\%$ we measured $A_{LL}=-0.0014\pm {0.0037}^{\mathrm{stat}}$ at the lowest $p_T^{\mathrm{reco}}$ bin ($4–5\mathrm{GeV}/c$) and $-0.0181\pm {0.0282}^{\mathrm{stat}}$ at the highest $p_T^{\mathrm{reco}}$ bin ($10–12\mathrm{GeV}/c$) with a beam polarization scale error of 9.4% and a $p_T$ scale error of 10%. Jets in the measured $p_T^{\mathrm{reco}}$ range arise primarily from hard-scattered gluons with momentum fraction $0.02<x<0.3$ according to pythia. The measured $A_{LL}$ is compared with predictions that assume various $\Delta G(x)$ distributions based on the Gluck-Reya-Stratmann-Vogelsang parameterization. The present result imposes the limit $-1.1<{\int }_{0.02}^{0.3}dx\Delta G(x,{\mu }^2=1{\mathrm{GeV}}^2)<0.4$ at 95% confidence level or ${\int }_{0.02}^{0.3}dx\Delta G(x,{\mu }^2=1{\mathrm{GeV}}^2)<0.5$ at 99% confidence level.

Quantum groups and noncommutative spaces have been repeatedly utilized in approaches to quantum gravity. They provide a mathematically elegant cutoff, often interpreted as related to the Planck-scale quantum uncertainty in position. We consider here a different geometrical interpretation of this cutoff, where the relevant noncommutative space is the space of directions around any spacetime point. The limitations in angular resolution express the finiteness of the angular size of a Planck-scale minimal surface at a maximum distance $1/\sqrt{\Lambda }$ related the cosmological constant $\Lambda$. This yields a simple geometrical interpretation for the relation between the quantum deformation parameter $q=e^{i\Lambda l_{\mathrm{Planck}}^2}$ and the cosmological constant, and resolves the difficulty of more conventional interpretations of the physical geometry described by quantum groups or fuzzy spaces.

The IIA superstring partition function $Z_{\mathrm{IIA}}$, on a Euclidean ${\mathrm{AdS}}_2\times S^2\times {\mathrm{CY}}_3$ computes the modified elliptic genus $Z_{\mathrm{BH}}$ of the associated black hole. The hybrid formalism of superstrings on ${\mathrm{AdS}}_2\times S^2$, defined as a sigma model on the coset supermanifold $PSU(1,1|2)/U(1)\times U(1)$ with a Wess-Zumino term, together with Calabi-Yau and chiral boson conformal field theories, is used to calculate the partition function of IIA superstrings on the Euclidean attractor geometry ${\mathrm{AdS}}_2\times S^2\times {\mathrm{CY}}_3$. Instead of the kappa symmetry analysis used by Beasely et al. in Ref. [33], we use world-sheet superconformal invariance to construct a nilpotent Becchi, Rouet, Stora, Tyutin (BRST) operator. The sigma model action is explicitly shown to be closed under this BRST operator. Localization arguments are then used to deform the world-sheet path integral with the addition of a BRST exact term, where contributions arise only from the center of ${\mathrm{AdS}}_2$ and the north and south poles of $S^2$. This leads to the Ooguri, Strominger, and Vafa result $Z_{\mathrm{BH}}=Z_{\mathrm{IIA}}=|Z_{\mathrm{top}}{|}^2$, where $|Z_{\mathrm{top}}{|}^2$ is the square of the topological string partition function.

The Schwarzschild–de Sitter and Reissner-Nordström–de Sitter black hole metrics appear as exact solutions in the recently formulated massive gravity of de Rham, Gabadadze and Tolley, where the mass term sets the curvature scale. They occur within a two-parameter family of de Rham, Gabadadze and Tolley mass terms. They show no trace of a cloud of scalar graviton modes, and in the limit of vanishing graviton mass they go smoothly to the Schwarzschild and Reissner-Nordström metrics.