Top pair production in the littlest Higgs model with T-parity

In the framework of the littlest Higgs model with T-parity,we study the top pair production at the next generation colliders like LHC and ILC.We find that the order O(αs) corrections to the standard model top pair production cross section at LHC can be very small and the magnitude is below 1%.However,the magnitude of corrections to the standard model top pair production rate at ILC may be over 5% for reasonable values'of the parameters.Besides this,the corrections to the asymmetry ALR(tt) may be more sizable. Therefore,the top pair production at ILC may serve as a probe of the littlest Higgs model with T-parity,especially the asymmetry ALR(tt).     

Update of the MCSANC Monte Carlo integrator,v. 1.20

New features of the MCSANC v.1.20 program, a Monte Carlo tool for calculation of the next-to-leading order electroweak and QCD corrections to various Standard Model processes, have been presented. The extensions concern implementation of Drell–Yan-like processes and include a systematic treatment of the photon-induced contribution in proton–proton collisions and electroweak corrections beyond the NLO approximation. There are also technical improvements such as calculation of the forward–backward asymmetry for the neutral current Drell–Yan process. The updated code is suitable for studies of the effects due to EW and QCD radiative corrections to Drell–Yan (and several other) processes at the LHC and for forthcoming high-energy proton–proton colliders.     

Large Hadron collider tests of the little Higgs model

The little Higgs model provides an alternative to traditional candidates for new physics at the TeV scale. The new heavy gauge bosons predicted by this model should be observable at the CERN Large Hadron Collider (LHC). We discuss how the LHC experiments could test the little Higgs model by studying the production and decay of these particles.     

Single top production associated with a neutral scalar at LHC in topcolor-assisted technicolor

The topcolor-assisted technicolor(TC2)model predicts a number of neutral SCalars like the top-pion (π0t)and the top-Higgs(h0t).These scalar8 have flavor-changing neutral-current(FCNC)top quark couphngs,among which the top-charm transition couplings may be sizable.Such FCNC couplings induce single top productions associated with a neutral scalar at the CERN Large Hadron Collider(LHC)through the parton processes cg→tπ0t and cg→th0t.In this paper we examine these productions and find their production rates can exceed the 3σ sensitivity of the LHC in a large part of parameter space.Since in the Standard Model and the minimal supersymmetric model such rare productions have unobservably small production rates at the LHC.these rare processes will serve as a good probe for the TC2 model.     

Exploring the Higgs portal

We study the Higgs portal from the Standard-Model to a hidden sector and examine which elements of the extended theory can be discovered and explored at the LHC. Our model includes two Higgs bosons covering parameter regions where the LHC will be sensitive to two, one or none of the particles at typical discovery luminosities for Standard Model Higgs production.     

Detecting Toppion via a Flavor-Changing Single Top Quark Production Process

In the framework of topcolor-assisted technicolor (TC2) theory, we study a flavor changing single top quarkproduction process pp(pp) →Ⅱ0t → tc(tc) at upgraded Tevatron and LHC. The results show that with the flavor changingcoupling of neutral toppion to top and charm quark, toppion provides a large te-channel resonance effect. The signal ofsingle top production could be detected at LHC. Otherwise, the narrow peak in the invariant mass distribution could beclearly detected both at upgraded Tevatron and LHC. Therefore, such single top production process provides a uniqueway to test TC2 model via the detection of tc-channel neutral toppion contribution.     

Little Higgs models and single top production at the LHC

We investigate the corrections of the “littlest” Higgs (LH) model and the SU(3) simple group model to single top production at the CERN Large Hadron Collider (LHC). We find that the new gauge bosons W_H ^± predicted by the LH model can generate significant contributions to single top production via the s-channel process. The correction terms for the tree-level Wqq’ couplings coming from the SU(3) simple group model can give large contributions to the cross sections of the t-channel single top production process. We expect that the effects of the LH model and the SU(3) simple group model on single top production can be detected at the LHC experiments.     

Electroweak Higgs boson production in the standard model effective field theory beyond leading order in QCD

We study the impact of dimension-six operators of the standard model effective field theory relevant for vector-boson fusion and associated Higgs boson production at the LHC. We present predictions at the next-to-leading order accuracy in QCD that include matching to parton showers and that rely on fully automated simulations. We show the importance of the subsequent reduction of the theoretical uncertainties in improving the possible discrimination between effective field theory and standard model results, and we demonstrate that the range of the Wilson coefficient values allowed by a global fit to LEP and LHC Run I data can be further constrained by LHC Run II future results.     

Measurements of the production, decay and properties of the top quark: a review

With the full Tevatron Run II and early LHC data samples, the opportunity for furthering our understanding of the properties of the top quark has never been more promising. Although the current knowledge of the top quark comes largely from Tevatron measurements, the experiments at the LHC are poised to probe top-quark production and decay in unprecedented regimes. Although no current top quark measurements conclusively contradict predictions from the standard model, the precision of most measurements remains statistically limited. Additionally, some measurements, most notably A _FB in top quark pair production, show tantalizing hints of beyond-the-Standard-Model dynamics. The top quark sample is growing rapidly at the LHC, with initial results now public. This review examines the current status of top quark measurements in the particular light of searching for evidence of new physics, either through direct searches for beyond the standard model phenomena or indirectly via precise measurements of standard model top quark properties.     

Top quark forward-backward asymmetry and same-sign top quark pairs

The top quark forward-backward asymmetry measured at the Tevatron collider shows a large deviation from standard model expectations. Among possible interpretations, a nonuniversal Z' model is of particular interest as it naturally predicts a top quark in the forward region of large rapidity. To reproduce the size of the asymmetry, the couplings of the Z' to standard model quarks must be large, inevitably leading to copious production of same-sign top quark pairs at the energies of the Large Hadron Collider (LHC). We explore the discovery potential for tt and ttj production in early LHC experiments at 7-8 TeV and conclude that if no tt signal is observed with 1 fb?1 of integrated luminosity, then a nonuniversal Z' alone cannot explain the Tevatron forward-backward asymmetry.     

Dark matter production at the LHC from black hole remnants

We study dark matter production at CERN LHC from black hole remnants (BHR). We find that the typical mass of these BHR at the LHC is ∼5–10 TeV which is heavier than other dark matter candidates, such as axion, axino, neutralino, etc. We propose the detection of this dark matter via single jet production in the process pp → jet + BHR (dark matter) at CERN LHC. We find that for zero impact parameter partonic collisions, the monojet cross section is not negligible in comparison to the standard model background and is much higher than the other dark matter scenarios studied so far. We also find that dσ/dp _T of jet production in this process increases as p _T increases, whereas in all other dark matter scenarios the dσ/dp _T decreases at CERN LHC. This may provide a useful signature for dark matter detection at the LHC. However, we find that when the impact parameter dependent effect of inelasticity is included, the monojet cross section from the above process becomes much smaller than the standard model background and may not be detectable at the LHC.     

Next-to-leading order QCD and electroweak corrections to Higgs-strahlung processes at the LHC

In this paper we calculate the total and fiducial cross sections as well as differential distributions for the Higgs-strahlung or VH process pp→VH→lv1/1~-1~++H,(V = W or Z, 1=e, μ) including QCD and electro-weak corrections up to next-to-leading order before and after reweighting photon PDFs of NNPDF2.3 qed, NNPDF3.0 qed,MRST2004 qed, CT14 QEDinc, and LUXqed at the LHC with 13 TeV and Higgs boson mass MH = 125 GeV. The predictions from the various photon PDFs before and after reweighting against each other are in good agreement.The photon PDF uncertainties of the photon-induced cross sections decrease significantly with the reweighting PDFs.     

ALICE perspectives for the study of charm and beauty energy loss at the LHC

At LHC energy, heavy quarks will be abundantly produced and the design of the ALICE detector will allow us to study their production using several channels. The expected heavy-quark in-medium energy loss in nucleus-nucleus collisions at the LHC is calculated within a model, that is compared to the available heavy-quark quenching measurements at RHIC. The nuclear modification factors and heavy-to-light ratios of charm and beauty mesons are considered. The capability of the ALICE experiment for addressing this phenomenology is discussed. PACS 25.75.-q; 14.65.Dw; 13.25.Ft     

On the photon production in nucleus-nucleus collisions at high energy

A modified Landau hydrodynamical model is applied to study hard thermal photon production in central heavy-ion collisions at LHC, RHIC and SPS energies. It is shown that the phase transition from quark-gluon plasma into hadrons in consequence of the thermodynamical expansion is close to the second order phase transition if a resonance production is taken into account. Hard direct photon emission is also investigated with consideration of nuclear shadowing effect on structure function of quarks and gluons. Also π^π photon background is investigated. It is demonstrated that at the LHC energy photon yield from the quark-gluon plasma in the photon transversal momentumk _⊥ range from 5 to 25 GeV/c exceeds both the background and the direct photon yield. This conclusion may be important for the quark-gluon plasma diagnostic aims. It is also shown that for the LHC energy the thermal photon yield in the present model essentially exceeds this yield obtained in the Bjorken scaling model.     

Single t-Quark Productions via Flavor-Changing Processes in Topcolor-Assisted Technicolor Model at Hadron Colliders

In the framework of topcolor-assisted technicolor （TC2） model, there exist tree-level flavor-changing （FC） couplings, which can result in the loop-level FC coupling tcg. Such tcg coupling can contribute significant clues at the forthcoming Large Hadron Collider （LHC） experiments. In this paper, based on the TC2 model, we study some single t-quark production processes involving tcg coupling at the Tevatron and LHC： pp（pp） → tq （q = u, d, s）, tg. We calculate the cross sections of these processes. The results show that the cross sections at the Tevatron are too small to observe the signal, but at the LHC it can reach a few pb. With the high luminosity, the LHC has considerable capability to find the single t-quark signal produced via some FC processes involving coupling tcg. On the other hand, these processes can also provide some valuable information of the coupling tcg with detailed study of the processes and furthermore provide the reliable evidence to test the TC2 model     

Probing the TC2 model via Production of Top Quark Pairs at Tevatron and LHC

The topcolour-assisted technicolour （TC2） model is an interesting dynamical theory among the various new physics models. We cMculate the total tt cross section and the relative correction of the TC2 model to the cross section at Tevatron Run Ⅱ and LHC. At the Tevatron Run Ⅱ, the cross section predicted by the standard model （SM） is consistent with the experimental data, and in most parameter spaces of the TC2 model, the relative correction of the TC2 model to the cross section is too small to be detectable. We find that the tt cross section is more sensitive to the parameters of the TC2 model at the LHC and the relative correction of the TC2 model to the cross section is over 10% in general. Such a value of the relative correction should be large enough to be detectable at the LHC. Therefore, it is promising to find the clue of the TC2 model via the tt production at the LHC.     

Associated ZH and WH Production in Left-Right Twin Higgs Model at LHC

At the CERN large hadron collider (LHC), production of the Higgs boson in association with Z or W bosons provides a dramatic experimental signal for detecting the standard model (SM) Higgs boson. In this paper, we consider the contributions of the left-right twin Higgs (LRTH) model to the processes q\bar{q}→Z(W)H. Our numerical results show that, in the favorable parameter spaces, the cross sections deviate distinctly from the predictions
of the SM. The possible signals of the LRTH model can be detected via these processes at the LHC experiments.     

Gauge boson pair production at the LHC: Anomalous couplings and vector boson scattering

We compare vector boson fusion and quark antiquark annihilation production of vector boson pairs at the LHC and include the effects of anomalous couplings. Results are given for confidence intervals for anomalous couplings at the LHC assuming that measurements will be in agreement with the standard model. We consider all couplings of the general triple vector boson vertex and their correlations. In addition we consider a gauge invariant dimension-six extension of the standard model. Analytical results for the cross sections for quark antiquark annihilation and vector boson fusion with anomalous couplings are given. Received: 24 June 1997 / Revised version: 10 November 1997 / Published online: 30 March 1998     

Measuring the Higgs boson self-coupling at the Large Hadron Collider

Inclusive standard model Higgs boson pair production and subsequent decay to same-sign dileptons via weak gauge W+/- bosons at the CERN Large Hadron Collider (LHC) has the capability to determine the Higgs boson self-coupling, lambda. The large top quark mass limit is found not to be a good approximation for the signal if one wishes to utilize differential distributions in the analysis. We find that it should be possible at the LHC with design luminosity to establish that the standard model Higgs boson has a nonzero self-coupling and that lambda/lambda(SM) can be restricted to a range of 0-3.7 at 95% confidence level if its mass is between 150 and 200 GeV.     

Bulk matter physics and its future at the Large Hadron Collider

Measurements at low transverse momentum will be performed at the LHC for studying particle production mechanisms in pp and heavy-ion collisions. Some of the experimental capabilities for bulk matter physics are presented, focusing on tracking elements and particle identification. In order to anticipate the study of baryon production for both colliding systems at multi-TeV energies, measurements for identified species and recent model extrapolations are discussed. Several mechanisms are expected to compete for hadro-production in the low momentum region. For this reason, experimental observables that could be used for investigating multi-parton interactions and help understanding the “underlying event” content in the first pp collisions at the LHC are also mentioned.