Narrow Results

In the context of topcolor-assisted techicolor (TC2) models, we study the lepton flavor violating (LFV) signals of the neutral scalars (the top-pion and the top-Higgs boson) at hadron colliders via considering their contribution to the processes (l = μ or e). We find that the LFV signals of these new particles cannot be detected at the Tevatron with , while might be observable in the future LHC with .

We study the associated production of the neutral top-pion with the third family quarks within the context of the topcolor-assisted technicolor model at the hadron colliders. The studies show that, at the Tevatron, the cross-sections of all these processes are too small to produce enough identified signals. But the cross-sections can be largely enhanced at the LHC. Specially for the processes and , the cross-sections can reach the level of a few hundred fb even a few pb for the light neutral top-pion. With the high yearly luminosity 100 fb^-1 at the LHC, over 10⁴ signals can be produced via the above two processes. There exists an ideal flavor-changing mode to detect neutral top-pion, i.e. , because the SM background of such production mode are very clean. Therefore, we can conclude that neutral top-pion should be observable at the LHC via the processes and . On the other hand, the statistics available at the LHC via these two processes might be enough to measure the Yukawa couplings and . Finally, it must be noted that the study of the process can give us a good chance to distinguish the TC2 model from the SM and MSSM because there does not exist such similar tree-level favor-changing process in these models.

Production of charged Higgs boson associated with a W gauge boson at the LHC is mainly induced by the tree-level annihilation and the one-loop gg fusion. In the context of the Higgs triplet model (HTM) and the left–right twin Higgs (LRTH) model, we calculate the production cross-section σ of the process pp→H^±W^∓ and compare our results with those given by supersymmetry (SUSY). We find that, in most of the parameter space of the HTM, the production cross-section σ is smaller than that predicted by the LRTH model or SUSY. The value of σ within the LRTH model is larger or smaller than the SUSY case, which depends on the relevant free parameters.

The $R_K$ measurement by LHCb suggests nonstandard Lepton-Universality Violation (LUV) to occur in $b\to s{\ell }^{+}{\ell }^{-}$ decays with effects in muons rather than electrons. It is intriguing that a number of other measurements of $b\to s{\ell }^{+}{\ell }^{-}$ transitions by LHCb and B-factories are consistent in magnitude and sign with the $R_K$ effect, and fit a coherent effective-theory picture. Further indications of nonstandard LUV are provided by the long-standing discrepancies in $b\to c\tau \nu$ transitions via the ratios $R(D)$ and $R(D^{\ast })$. We review in detail the experimental situation and its rich outlook, the theoretical efforts — and their challenges — towards convincing dynamics beyond the effective-theory level, and discuss the many directions of further investigation that propagate from the current situation.

The impact of higher-order matrix elements and ${\mu }_R$ and ${\mu }_F$ scales on the NLO K factors for ZZ vector boson pairs in proton–proton collisions are presented in this study. All predictions are performed using MCFM-8.0 Monte Carlo generator. First, the QCD predictions of ZZ production at LO and NLO accuracies are obtained using two most recent PDFs, MMHT2014 and CT14. To discuss the impact of higher-order matrix elements on the NLO K factors, both LO and NLO corrections are obtained by LO, NLO and NNLO matrix elements of these two most recent PDFs. Then, the impact of ${\mu }_R$ and ${\mu }_F$ scales on the NLO K factors are further discussed by using six different values of ${\mu }_R$ and ${\mu }_F$ in a range of $\frac{1}{2}{M}_Z\le {\mu }_R$, ${\mu }_F\le 2M_Z$, where $M_Z$ is Z boson mass.

In the framework of the singly charged scalar singlet model, we study the possibility of detecting the singly charged $\mathrm{\text{SU}}{(2)}_L$ singlet scalar S through the Drell–Yan process at the High-Luminosity-Large Hadron Collider (HL-LHC) with the center-of-mass energy $\sqrt{s}=14\mathrm{\text{TeV}}$ and the integrated luminosity $\mathcal{ℒ}=3{\mathrm{\text{ab}}}^{-1}$, the High-Energy-Large Hadron Collider (HE-LHC) with $\sqrt{s}=27\mathrm{\text{TeV}}$ and $\mathcal{ℒ}=10{\mathrm{\text{ab}}}^{-1}$ as well as the Future Circular Collider — hadron–hadron (FCC-hh) with $\sqrt{s}=100\mathrm{\text{TeV}}$ and $\mathcal{ℒ}=20{\mathrm{\text{ab}}}^{-1}$. Considering the constraints on the free parameters, after performing a detector level simulation for the signals and relevant backgrounds, we find that the scalar S might be detected in a certain range of the parameter space, which is not excluded by the current constraints.

The model-independent constraints on the Abelian Z′ couplings from the LEP data are applied to estimate the Z′ production in experiments at the Tevatron and LHC. The Z′ total and partial decay widths are analyzed. The results are compared with model-dependent predictions and present experimental data from the Tevatron. If we assume the 1–2σ hints from the LEP data to be a signal of the Abelian Z′ boson, then the Tevatron data constrain the Z′ mass between 400 GeV and 1.2 TeV.

We review tools that have been developed in recent years to maximize our ability to discover and characterize new physics appearing in LHC events with missing transverse momentum.

Thanks to the latest development in the field of Monte Carlo event generators and satellite programs allowing for a straightforward implementation of any beyond the Standard Model theory in those tools, studying the property of any softly-broken supersymmetric theory is become an easy task. We illustrate this statement in the context of two nonminimal supersymmetric theories, namely the Minimal Supersymmetric Standard Model with R-parity violation and the Minimal R-symmetric Supersymmetric Standard Model and choose to probe interaction vertices involving a nonstandard color structure and the sector of the top quark. We show how to efficiently implement these theories in the MATHEMATICA package FEYNRULES and use its interfaces to Monte Carlo tools for phenomenological studies. For the latter, we employ the latest version of the MADGRAPH program.

In this paper, we investigate the Drell–Yan process with the intermediate heavy Z′ boson. We use a general approach to the Abelian Z′ that utilizes the renormalization-group relations between the Z′ couplings and allows to reduce the number of unknown Z′ parameters significantly. In a newly proposed strategy, we estimate the LHC-driven constraints for the Z′ couplings to lepton and quark vector currents. To do this, we calculate the Z′-related contribution in the narrow-width approximation and compare the obtained values to the experimental data presented by the ATLAS and CMS collaborations. Our method allows to estimate the values of Z′ couplings to the u and d quarks and to final-state leptons.

Opening Lecture at the Hong Kong University of Science and Technology Jockey Club Institute for Advanced Study Program on High Energy Physics Conference, January 18–21, 2016.

Superconducting magnets have played a key role in advancing the energy reach of proton synchrotrons and enabling them to play a major role in defining the Standard Model. The problems encountered and solved at the Tevatron are described and used as an introduction to the many challenges posed by the use of this technology. The LHC is being prepared to answer the many questions beyond the Standard Model and in itself is at the cutting edge of technology. A description of its magnets and their properties is given to illustrate the advances that have been made in the use of superconducting magnets over the past 30 years.

Simon van der Meer was a brilliant scientist and a true giant of accelerator science. His seminal contributions to accelerator science have been essential to this day in our quest for satisfying the demands of modern particle physics. Whether we talk of long base-line neutrino physics or antiproton–proton physics at Fermilab or proton–proton physics at LHC, his techniques and inventions have been a vital part of the modern day successes. Simon van der Meer and Carlo Rubbia were the first CERN scientists to become Nobel laureates in Physics, in 1984. Van der Meer's lesser-known contributions spanned a whole range of subjects in accelerator science, from magnet design to power supply design, beam measurements, slow beam extraction, sophisticated programs and controls.

Superconducting Magnets for High Energy Physics Accelerators are entering a new era. The successful operation of the LHC in the last decade has marked the summit of the Nb-Ti technology exploitation initiated by the Tevatron. Now, after two decades of development, Nb₃Sn technology for accelerators is becoming mature and the construction of the high luminosity LHC (HL-LHC) magnets will be the most tangible sign of the new phase, with magnets that will operate well beyond the symbolic threshold of 10 T. In addition, 30 years after its discovery, the high temperature superconductors (HTSs) for accelerator magnets are under development and test, to understand if these materials can enable the 20 T range for next accelerator/colliders foreseen after 2030. The paper reviews the main issues and the criticalities of the magnets’ development for the next future project, HL-LHC, and gives the prospect for the design and technological effort that is underway in magnet technology for the energy Frontier (FCC/HE-LHC).

We review and discuss the use of TMD, or "unintegrated", gluon distributions in the domain of small-x physics. The definitions employed, and the hazards of the naive applications of the TMD factorization and the associated gluon distributions are discussed.

Superconducting Magnets for High Energy Physics Accelerators are entering a new era. The successful operation of the LHC in the last decade has marked the summit of the Nb-Ti technology exploitation initiated by the Tevatron. Now, after two decades of development, Nb₃Sn technology for accelerators is becoming mature and the construction of the high luminosity LHC (HL-LHC) magnets will be the most tangible sign of the new phase, with magnets that will operate well beyond the symbolic threshold of 10 T. In addition, 30 years after its discovery, the high temperature superconductors (HTSs) for accelerator magnets are under development and test, to understand if these materials can enable the 20 T range for next accelerator/colliders foreseen after 2030. The paper reviews the main issues and the criticalities of the magnets’ development for the next future project, HL-LHC, and gives the prospect for the design and technological effort that is underway in magnet technology for the energy Frontier (FCC/HE-LHC).

We study the collider phenomenology of a Littlest Higgs model with T-parity (LHT). We stress the crucial role of the T-odd SU(2) doublet fermions providing the consistence of the theory and leading to excited phenomenology at the LHC.

Superconducting magnets have played a key role in advancing the energy reach of proton synchrotrons and enabling them to play a major role in defining the Standard Model. The problems encountered and solved at the Tevatron are described and used as an introduction to the many challenges posed by the use of this technology. The LHC is being prepared to answer the many questions beyond the Standard Model and in itself is at the cutting edge of technology. A description of its magnets and their properties is given to illustrate the advances that have been made in the use of superconducting magnets over the past 30 years.

The High Luminosity LHC is one of the major scientific project of the next decade. It aims at increasing the luminosity reach of LHC by a factor five for peak luminosity and a factor ten in integrated luminosity. The project, now fully approved and funded, will be finished in ten years and will prolong the life of LHC until 2035-2040. It implies deep modifications of the LHC for about 1.2 km around the high luminosity insertions of ATLAS and CMS and relies on new cutting edge technologies. We are developing new advanced superconducting magnets capable of reaching 12 T field; superconducting RF crab cavities capable to rotate the beams with great accuracy; 100 kA and hundred meter long superconducting links for removing the power converter out of the tunnel; new collimator concepts, etc… Beside the important physics goals, the High Luminosity LHC project is an ideal test bed for new technologies for the next hadron collider for the post-LHC era.

Opening Lecture at the Hong Kong University of Science and Technology Jockey Club Institute for Advanced Study Program on High Energy Physics Conference, January 18–21, 2016.