119114878
1-Jettiness in DIS: Measuring 2 Jets in 3 Ways
We compute cross sections for two-jet production in deep inelastic scattering (DIS), with one jet from initial state radiation (ISR) and the other from final state radiation, with a summation of large logarithms up to next-to-next-to-leading logarithmic (NNLL) accuracy. Use of the DIS event shape 1-jettiness ensures that events have two well-collimated jets. We calculate distributions for three versions of 1-jettiness that have different sensitivity to the transverse momentum of the ISR, and derive factorization theorems for each of them using the soft collinear effective theory (SCET). The structure of the transverse momentum dependence in the factorization theorems is different for each 1-jettiness. We present numerical results for these three observables with parameters for the HERA collider.
119187963
Jet shapes and jet algorithms in SCET
Jet shapes are weighted sums over the four-momenta of the constituents of a jet and reveal details of its internal structure, potentially allowing discrimination of its partonic origin. In this work we make predictions for quark and gluon jet shape distributions in N-jet final states in e+e− collisions, defined with a cone or recombination algorithm, where we measure some jet shape observable on a subset of these jets. Using the framework of Soft-Collinear Effective Theory, we prove a factorization theorem for jet shape distributions and demonstrate the consistent renormalization-group running of the functions in the factorization theorem for any number of measured and unmeasured jets, any number of quark and gluon jets, and any angular size R of the jets, as long as R is much smaller than the angular separation between jets. We calculate the jet and soft functions for angularity jet shapes τα to one-loop order $ \left( {\mathcal{O}\left( {{\alpha_s}} \right)} \right) $ and resum a subset of the large logarithms of τα needed for next-to-leading logarithmic (NLL) accuracy for both cone and kT-type jets. We compare our predictions for the resummed τα distribution of a quark or a gluon jet produced in a 3-jet final state in e+e− annihilation to the output of a Monte Carlo event generator and find that the dependence on a and R is very similar.
119204877
Consistent Factorization of Jet Observables in Exclusive Multijet Cross-Sections
Abstract We demonstrate the consistency at the next-to-leading-logarithmic (NLL) level of a factorization theorem based on Soft-Collinear Effective Theory (SCET) for jet shapes in e + e − collisions. We consider measuring jet observables in exclusive multijet final states defined with cone and k T -type jet algorithms. Consistency of the factorization theorem requires that the renormalization group evolution of hard, jet, and soft functions is such that the physical cross section is independent of the factorization scale μ . The anomalous dimensions of the various factorized pieces, however, depend on the color representation of jets, choice of jet observable, the number of jets whose shapes are measured, and the jet algorithm, making it highly nontrivial to satisfy the consistency condition. We demonstrate the intricate cancellations between anomalous dimensions that occur at the NLL level, so that, up to power corrections that we identify, our factorization of the jet shape distributions is consistent for any number of quark and gluon jets, for any number of jets whose shapes are measured or unmeasured, for any angular size R of the jets, and for any of the algorithms we consider. Corrections to these results are suppressed by the SCET expansion parameter λ (set by the ratio of the typical momentum in a jet transverse to the jet axis to the total jet energy) and in the jet separation measure 1 / t 2 = tan 2 ( R / 2 ) / tan 2 ( ψ / 2 ) , where ψ is the angular separation between jets. Our results can be used to calculate a wide variety of jet observables in multijet final states to NLL accuracy.
26881716
Resonant relaxation in electroweak baryogenesis
We compute the leading, chiral charge-changing relaxation term in the quantum transport equations that govern electroweak baryogenesis using the closed time path formulation of nonequilibrium quantum field theory. We show that the relaxation transport coefficients may be resonantly enhanced under appropriate conditions on electroweak model parameters and that such enhancements can mitigate the impact of similar enhancements in the CP-violating source terms. We also develop a power counting in the time and energy scales entering electroweak baryogenesis and include effects through second order in ratios epsilon of the small and large scales. We illustrate the implications of the resonantly enhanced [script O](epsilon 2) terms using the Minimal Supersymmetric Standard Model, focusing on the interplay between the requirements of baryogenesis and constraints obtained from collider studies, precision electroweak data, and electric dipole moment searches.
118867883
Enhanced nonperturbative effects in Z decays to hadrons
We use soft collinear effective field theory (SCET) to study nonperturbative strong interaction effects in Z decays to hadronic final states that are enhanced in corners of phase space. These occur, for example, in the jet energy distribution for two jet events near E_J=M_Z/2, the thrust distribution near unity and the jet invariant mass distribution near zero. The extent to which such nonperturbative effects for different observables are related is discussed.
122534296
Peeking inside jets for clues of new physics
Observables probing jet structure and substructure help uncover clues about the energetic particles which originated them, such as ordinary light quarks and gluons or from decays of heavy particles in and beyond the Standard Model. This talk overviews such recently introduced methods.
16162020
Boson Stars with Self-Interacting Quantum Scalar Fields
The Klein-Gordon-Einstein equations of classical real scalar fields have time-dependent solutions (periodic in time). We show that quantum real scalar fields can form non-oscillating (static) solitonic objects, which are quite similar to the solutions describing boson stars formed with classical and quantum complex scalar fields (the latter will be studied in this paper). We numerically analyze the difference between them concerning the mass of boson stars. On the other hand, we suggest an interesting test (a viable process that the boson star may undergo in the early universe) for the formation of boson stars. That is, it is questioned that after a second-order phase transition (a simple toy model will be considered here), what is the fate of the boson star composed of quantum real scalar field.
2435715
Late time behaviors of an inhomogeneous rolling tachyon
We study an inhomogeneous decay of an unstable D-brane in the context of Dirac-Born-Infeld (DBI)-type effective action. We consider tachyon and electromagnetic fields with dependence of time and one spatial coordinate, and an exact solution is found under an exponentially decreasing tachyon potential, e{sup -|T|/{radical}}{sup (2)}, which is valid for the description of the late time behavior of an unstable D-brane. Though the obtained solution contains both time and spatial dependence, the corresponding momentum density vanishes over the entire spacetime region. The solution is governed by two parameters. One adjusts the distribution of energy density in the inhomogeneous direction, and the other interpolates between the homogeneous rolling tachyon and static configuration. As time evolves, the energy of the unstable D-brane is converted into the electric flux and tachyon matter.
119386984
AXION EMISSIVITY FROM THE CONVERSION OF A NEUTRON STAR INTO A STRANGE STAR
Abstract The conversion of neutron matter into strange matter in a neutron star occurs through the non-leptonic weak-interaction process. We study the energy loss of the neutron star by the emission of axions in that process. Owing to that process, the neutron star will liberate the energy which can in no way be negligible as an axion burst.
17997328
Diffuse gamma-ray background and primordial black hole constraints on the spectral index of density fluctuations
We calculate the flux of $\ensuremath{\gamma}$ rays emitted from primordial black holes (PBHs) which are formed by a ``blue'' power-law spectrum of density fluctuations in the early universe. Gamma-ray emission from such PBHs may contribute significantly to the observed extragalactic diffuse $\ensuremath{\gamma}$-ray background (DGB). Using the observed DGB flux from the imaging Compton Telescope (COMPTEL) and the Energetic Gamma Ray Experiment Telescope (EGRET) as the upper limit of $\ensuremath{\gamma}$-ray flux from PBHs, we derive the upper limit on the spectral index n of the density fluctuations. The range of initial PBH masses which can contribute to the DGB is $2\ifmmode\times\else\texttimes\fi{}{10}^{13} \mathrm{g}\ensuremath{-}5\ifmmode\times\else\texttimes\fi{}{10}^{14} \mathrm{g},$ corresponding to a cosmic reheating temperature of $7\ifmmode\times\else\texttimes\fi{}{10}^{7} \mathrm{GeV}\ensuremath{-}4\ifmmode\times\else\texttimes\fi{}{10}^{8} \mathrm{GeV}.$ In this range, we find the upper limit to be $n\ensuremath{\lesssim}1.23\ensuremath{-}1.25.$ This limit is stronger than those derived from the energy density in PBHs or PBH relics and matches the value of n required to explain the cosmic microwave background anisotropy.
1357101
Pulsar magnetospheres: a general relativistic treatment
A fully general relativistic description of pulsar magnetospheres is provided. To be more specific, a study of pulsar magnetospheres is performed in the context of general relativistic magnetohydrodynamics (MHD) employing the so-called Grad–Shafranov approach. Not surprisingly, the resulting Grad–Shafranov equations and all the other related general relativistic MHD equations turn out to take essentially the same structures as those for a (rotating) black hole magnetosphere. Other different natures between the two cases including the structure of singular surfaces of MHD flows in each magnetosphere are essentially encoded in the different space–time (metric) contents. In this way, pulsar and black hole magnetospheres can be described in a unified fashion. Particularly, the direction of poloidal currents circulating in the neutron star magnetosphere turns out to be the same as that of currents circulating in a black hole magnetosphere, which in turn leads to pulsar and black hole spin-down via ‘magnetic braking’.