In this note a study of hadronic event shapes in QCD events at the Large Hadron Collider (LHC) is presented. Calorimetric jet momenta, determined by various jet clustering algorithms, are used as input for calculating various event-shape variables which probe the structure of the hadronic final state. It is shown that the normalized event-shape distributions are robust under variations of the jet energy scale and resolution effects, which makes them particularly suitable for early data analysis and tuning of Monte Carlo models.
We present definite correlations between the CMS 5 \fb all-hadronic search employing the stransverse mass variable $M_{T2}$ and the ATLAS 5 \fb all-hadronic and multijet supersymmetry (SUSY) searches, suggesting the possibility that both the ATLAS and CMS experiments are already registering a faint but legitimate SUSY signal at the LHC. We isolate this prospective mutual productivity beyond the Standard Model in the framework of the supersymmetric No-Scale Flipped $SU$(5) grand unified theory, supplemented with extra vector-like matter (flippons). Evident overproduction is observed in three CM…
We discuss the possibility of quantum entanglement for pairs of charged particles produced in high-energy $pp$-collisions at the LHC. Using a framework of interacting Wilson lines, we calculate 2-D and 1-D two-particle angular correlation functions in terms of the differences of the pseudorapidities and azimuthal angles of the produced particles. The calculated near-side angular correlation shows a localized maximum around $Δϕ\approx 0$, though it is less pronounced compared to the peak observed by the CMS Collaboration. We argue that this soft correlation is universal and insensitive to the s…
We present the medium-modified energy collimation in the leading-logarithmic approximation (LLA) and next-to-leading-logarithmic approximation (NLLA) of QCD. As a consequence of more accurate kinematic considerations in the argument of the Dokshitzer-Gribov-Lipatov-Altarelli-Parisi (DGLAP) fragmentation functions (FFs) we find a new NLLA correction ${\cal O}(α_s)$ which accounts for the scaling violation of DGLAP FFs at small $x$. The jet shape is derived from the energy collimation within the same approximations and we also compare our calculations for the energy collimation with the event ge…
Results of searches for SUSY production at CMS in events with third-generation signatures are presented. Along with missing energy, the final states may include hadronic jets with or without b-quark tag, light leptons, and tau leptons. These features serve both to distinguish standard-model components, and sensitivity to those SUSY models that lead to final states rich of heavy-flavored particles.
The inclusive production at the LHC of a charged light hadron and of a jet, featuring a wide separation in rapidity, is suggested as a new probe process for the investigation of the BFKL mechanism of resummation of energy logarithms in the QCD perturbative series. We present some predictions, tailored on the CMS and CASTOR acceptances, for the cross section averaged over the azimuthal angle between the identified jet and hadron and for azimuthal correlations.
Hadronic event shapes, that is, event shapes at hadron colliders, could provide a great way to test both standard and non-standard theoretical models. However, they are significantly more complicated than event shapes at e+e- colliders, involving multiple hard directions, multiple channels and multiple color structures. In this paper, hadronic event shapes are examined with Soft-Collinear Effective Theory (SCET) by expanding around the dijet limit. A simple event shape, threshold thrust, is defined. This observable is global and has no free parameters, making it ideal for clarifying how resumm…
We report on a recent calculation of the electroweak O(α^3α_s) corrections to 3-jet production and related event-shape observables at e+e- colliders. The calculation properly accounts for the experimental photon isolation criteria and for the corrections to the total hadronic cross section. Corrections to the normalised event-shape distributions, which are exemplarily discussed here for the thrust distribution at LEP and linear-collider energies, turn out to be at the few-per-cent level and show remnants of the radiative return to the Z pole even after inclusion of appropriate cuts.
The LHCb detector provides accurate vertex reconstruction and hadronic particle identification, which make the experiment an ideal place to look for light long-lived particles (LLP) decaying into Standard Model (SM) hadrons. In contrast with the typical search strategy relying on energetic jets and a high multiplicity of tracks from the LLP decay, LHCb can identify LLPs in exclusive, specific hadronic final states. To illustrate the idea, we study the sensitivity of LHCb to an exotic Higgs decay $h\to SS$, followed by the displaced decay of GeV-scale scalars into charged kaons $S\to K^+K^-$. W…
We present a complete calculation of the electroweak O(alpha^3 alpha_s) corrections to three-jet production and related event-shape observables at electron--positron colliders. The Z-boson resonance is described within the complex-mass scheme, rendering the calculation valid both in the resonance and off-shell regions. Higher-order initial-state radiation is included in the leading-logarithmic approximation. We properly account for the corrections to the total hadronic cross section and for the experimental photon isolation criteria. To this end we implement contributions of the quark-to-photo…
The concept of Universal Shower Profile is used to characterize the average behavior of high energy cosmic rays. The shape variables contain important information about composition. They are independent of the primary cross-section by construction, but affected by other hadronic parameters, like multiplicity. The two variables give access to the average nuclear mass of the sample and their compatibility serves as a test of hadronic models.
We give an overview of our calculation of the next-to-next-to-leading order (NNLO) QCD corrections to W + jet production in hadronic collisions. Phenomenological results for multiple differential distributions are compared to CMS data for 8 TeV proton-proton collisions. We further discuss the application of the calculation to the transverse momentum spectrum of inclusive W boson production, again accompanied by a comparison to 8 TeV CMS data. In both cases, the inclusion of NNLO QCD effects give an improved agreement between theory and data with considerably reduced scale uncertainties with re…
We present a determination of the strong coupling constant from a fit of QCD predictions for six event-shape variables, calculated at next-to-next-to-leading order (NNLO) and matched to resummation in the next-to-leading-logarithmic approximation (NLLA). These event shapes have been measured in e+e- annihilations at LEP, where the data we use have been collected by the ALEPH detector at centre-of-mass energies between 91 and 206 GeV. Compared to purely fixed order NNLO fits, we observe that the central fit values are hardly affected, but the systematic uncertainty is larger because the NLLA pa…
We study the six classical event-shape observables in hadronic Higgs decays at next-to-leading order in QCD. To this end, we consider the decay of on-shell Higgs bosons to three partons, taking into account both the Yukawa-induced decay to $\mathrm{b}$-quark pairs and the loop-induced decay to two gluons via an effective Higgs-gluon coupling. The results are discussed with a particular focus on the discriminative power of event shapes regarding these two classes of processes.
We propose a novel idea for probing the Higgs boson couplings through the measurement of hadronic event shape distributions in the decay of the Higgs boson at lepton colliders. The method provides a unique test of the Higgs boson couplings and of QCD effects in the decay of the Higgs boson. It can be used to probe the Yukawa couplings of the light quarks and to further test the mechanism of electroweak symmetry breaking. From a case study for the proposed Circular Electron-Positron Collider, assuming a hypothesis of SM-like theory, light-quark couplings with a strength greater than 9% of the b…
We determine the likelihood distribution for the model parameters describing the event-by-event fluctuating proton geometry at small $x$ by performing a Bayesian analysis within the Color Glass Condensate framework. The exclusive $\mathrm{J}/ψ$ production data from HERA is found to constrain the model parameters well, and we demonstrate that complementary constraints can be obtained from simulations of Pb+Pb collisions at the LHC.
Experimental falsification or validation of the Standard Model of Particle Physics involves the measurement of the CP quantum number and couplings of the Higgs boson. Both ATLAS and CMS have reported an SM Higgs-like excess around m_H=125 GeV. In this mass range the properties of the Higgs boson can be extracted from an analysis of the azimuthal angle distribution of the two jets in pp->Hjj events. This channel is also important to measure the couplings of the Higgs boson to electroweak gauge bosons and fermions, hereby establishing the exceptional role of the Higgs boson in the Standard Model…
Analysis is presented for first moments of collective observable distributions in two-jet events for various interaction types and for wide initial energy range. These variables include sphericity, thrust, components of transverse particle momentum, alignment and planarity. Analytical functions are suggested for description of energy dependence for all collective variables under study with exception of infrared-stable thrust variable. Energy dependence for average thrust is compared with predictions of dispersive model and single dressed gluon approximation. Estimations of strong coupling cons…
Soft-drop grooming of hadron-collision final states has the potential to significantly reduce the impact of non-perturbative corrections, and in particular the underlying-event contribution. This eventually will enable a more direct comparison of accurate perturbative predictions with experimental measurements. In this study we consider soft-drop groomed dijet event shapes. We derive general results needed to perform the resummation of suitable event-shape variables to next-to-leading logarithmic (NLL) accuracy matched to exact next-to-leading order (NLO) QCD matrix elements. We compile predic…
We have revisited the prospects of Supersymmetry(SUSY) searches at the LHC with 7 TeV energy along with the prediction of the discovery potential at 8 TeV energy assuming an integrated luminosity 5 $fb ^{-1}$ and 20 $\invfb$ with mSUGRA/CMSSM as a model framework. We discuss further optimization of our selection strategy which is based on the hadronic event shape variables. Evaluating the standard model backgrounds and signal rates in detail we predict the discovery reach in the $m_0 - m_{1/2}$ plane for 7 TeV with 5$\invfb$ luminosity. We also present the discovery reach for 8 TeV energy with…
