QCD resummation for jet substructures

We provide a novel development in jet physics by predicting the energy profiles of light-quark and gluon jets in the framework of perturbative QCD. Resumming large logarithmic contributions to all orders in the coupling constant, our predictions are shown to agree well with Tevatron CDF and Large Hadron Collider CMS data. We also extend our resummation formalism to the invariant mass distributions of light-quark and gluon jets produced in hadron collisions. The predicted peak positions and heights in jet mass distributions are consistent with CDF data within uncertainties induced by parton distribution functions.     

Factorization and resummation for jet broadening

Jet broadening is an event-shape variable probing the transverse momenta of particles inside jets. It has been measured precisely in e⁺e⁻ annihilations and is used to extract the strong coupling constant. The factorization of the associated cross section at small values of the broadening is afflicted by a collinear anomaly. Based on an analysis of this anomaly, we present an all-order factorization theorem for jet-broadening distributions, which is free of large perturbative logarithms in the two-jet limit. Our formula reproduces known results at next-to-leading logarithmic order but also extends to higher orders.     

Understanding jet scaling and jet vetos in Higgs searches

Jet counting and jet vetos are crucial analysis tools for many LHC searches. We can understand their properties from the distribution of the exclusive number of jets. LHC processes tend to show either a distinct staircase scaling or a Poisson scaling, depending on kinematic cuts. We illustrate our approach in a detailed study of jets in weak boson fusion Higgs production.     

Gluinos and lower bounds for squark and slepton masses from jet plus missing-pT events at the pp collider

On the basis of a detailed phenomenological analysis, combined with the minimal N = 1 supergravity model, it is shown that the jet plus missing-p_T events at the p$\text{p}$ collider can only be explained by relatively light gluinos ($\text{m}\text{g}\text{?}\text{< m}\text{q}\text{?}$ with a mass of about 40 GeV. The resulting squark and slepton masses are then found to be $\text{q}\text{?}\text{> 50}$ GeV and $\text{m}\text{e}\text{?}\text{> 35}$ GeV.     

Effects of threshold resummation

We investigate effects of threshold resummation of logarithmic corrections lnN in Mellin space quantitatively. Threshold resummation leads to enhancement of next-to-leading-order QCD predictions for jet production at large jet transverse energy, which is in the trend indicated by experimental data. We show that this enhancement is completely determined by the behavior of threshold resummation at small N, the region where hierarchy among different powers of lnN is lost and current next-to-leading-logarithm resummation is not reliable. Our analysis indicates that more accurate threshold resummation formalism should be developed in order to obtain convincing predictions.     

LHC prospects in searches for neutral scalars in pp → γγ + jet

At hadron colliders, the γγ + jet channel provides a larger signal-to-background ratio in comparison with the inclusive γγ channel in hunting for scalars uncharged under the SM gauge group. By using NLO results for the SM Higgs boson production and corresponding background, we estimate LHC prospects in searches for the radion and sgoldstino in the γγ + jet channel. Three-body final-state kinematics allows for refined cuts. We have found that this channel could be comparable with the γγ channel in searches for new physics. The text was submitted by the authors in English.     

The resummation of one particle lines

We propose a partial resummation for a weak coupling cluster expansion. The resummation gives one particle lines with in/out field propagators. We give a Bethe-Salpeter equation in which one particle subtractions are defined using physical one particle states. By these methods, we show thatP()₂ quantum fields in the weak coupling region have only isolated bound state spectrum below the 2m threshold. HereP is not restricted to be even.Supported in part by the National Science Foundation under Grants PHY 78-08066 and PHY 77-18762. Both authors thank the I.H.E.S., Bures-sur-Yvette, and A. J. thanks C.E.N., Saclay, for their hospitality.     

Photino pair creation in a magnetic field and astrophysical limits on slepton mass

The photino pair creation by a charged lepton in an external magnetic field is studied. New bounds on the slepton mass are obtained by analyzing the role of this process in the theory of stellar evolution. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 5 305–308 (10 March 1996)     

Impact on soft sand: void collapse and jet formation

Very fine sand is prepared in a well-defined and fully decompactified state by letting gas bubble through it. After turning off the gas stream, a steel ball is dropped on the sand. On impact of the ball, sand is blown away in all directions ("splash") and an impact crater forms. When this cavity collapses, a granular jet emerges and is driven straight into the air. A second jet goes downwards into the air bubble entrained during the process, thus pushing surface material deep into the ground. The air bubble rises slowly towards the surface, causing a granular eruption. In addition to the experiments and the discrete particle simulations we present a simple continuum theory to account for the void collapse leading to the formation of the upward and downward jets.     

Impact of wall rotation on supraglottal jet stability in voiced speech

Supraglottal jet variability was investigated in a scaled-up flow facility incorporating driven vocal fold models with and without wall rotation. Principle component analysis was performed on the experimental supraglottal flow fields to ascertain the roll of glottal wall motion on the development of the supraglottal jet. It is shown that intraglottal flow asymmetries that develop due to wall rotation are not the primary mechanism for generating large-scale cycle-to-cycle deflection of the supraglottal jet. However, wall rotation does decrease the energy content of the first mode, redistributing it to the higher modes through an increase in unstructured flow variability.     

Comment on resummation of mass distribution for jets initiated by massive quarks

We compute in the heavy quark effective theory the soft coefficient D₂ entering the resummation of next-to-next-to-leading threshold logarithms for jets initiated by a quark with a small mass compared to the hard scale of the process. We find complete agreement with a previous computation in full QCD. Contrary to our previous guess, this coefficient turns out to be different from that one entering heavy flavor decay or heavy flavor fragmentation.     

New results on sterile neutrinos searches

New results on sterile neutrinos searches in kaon decays and neutrino oscillation experiments are presented.