8 pages, 5 tables, 1 figure. Presented at the International Workshop on Top Quark Physics (TOP2008), La Biodola, Isola d'Elba, Italy, May 2008. To be published in "Il nuovo cimento"
High-energy photon-proton interactions at the LHC offer interesting possibilities for the study of top properties. Using a fast simulation of a LHC-like detector, first results on the measurement of the |V_{tb}| matrix element using Wt photoproduction are presented. Anomalous photoproduction of single top due to Flavour-Changing Neutral Currents permits to improve the current limits on the coupling parameters, k_{tuγ} and k_{tcγ} after only 1 fb^{-1}.
The exclusive $Υ$ photoproduction in ultraperipheral proton-nucleus and nucleus-nucleus collisions at LHC energies is being investigated using pQCD framework which constrain the gluon distribution in the proton and nuclei at low $x$. Rapidity distributions of $Υ$ photoproduction with different gluon distribution parameterization and gluon shadowing for nuclear PDFs including photon flux suppression for strong interaction, are being presented at LHC energies. Predictions done for ultraperipheral collisions at $\sqrt s$=$8.16$ TeV in pPb, and at $\sqrt s$=$5.02$ TeV in PbPb collisions which are …
The cross section for exclusive $Υ$ ultraperipheral photoproduction at present and future colliders is determined using the low $x$ gluon PDF extracted from an analysis of exclusive $J/ψ$ measurements performed at HERA and the LHC. Predictions are given at next-to-leading order in collinear factorisation over a wide $γp$ centre-of-mass energy range, calculated assuming the non-relativistic approximation for the $Υ$ wave function, and with skewing corrections incorporated.
Precise photoproduction of the charged top-pions at the LHC with forward detector acceptances
在14台$LHC$（$TeV$）大型强子对撞机上研究了顶三角驼鹿（$TTM$）模型（顶色辅助的人工色$TC2$模型的一个解构版本）通过过程$pp\rightarrow p γp \rightarrow π^\pm_t t +X$预测的带电top-pion的光生，包括次领先阶（$NLO$）$QCD$修正.结果表明，产生截面和分布对自由参数$\sinω$和$M_{π_t}$敏感。典型的$QCD$校正值为$7\% \sim 11\%$，并且不太依赖于$\sinω$以及前向探测器接受度。
The $J/ψ$ production originating from elastic and inelastic photoproduction processes in p-p collisions at LHC energies is investigated, where the fragmentation processes are involved. An exact treatment is performed, which adopts the Martin-Ryskin method to weight the contribution from different channels, and can return to Weizsäcker-Williams approximation (WWA) when $Q^{2}\rightarrow0$. The relevant kinematical relations are also achieved. We present a comprehensive analysis for the feature of WWA by comparing with the exact treatment. The results are expressed in $Q^{2}$, $y$, $z$, $p_{T}$,…
We calculate the photoproduction of double $J/ψ$ ($Υ$) to leading order based on the nonrelativistic quantum chromodynamics factorization framework at the Large Hadron Collider with forward proton tagging. The numerical results of double $J/ψ$ photoproduction pp $\rightarrow$ p$γ$p $\rightarrow$ $J/ψ$ + $J/ψ$ with different forward detector acceptances ($ξ$) are presented. The total cross section of double $J/ψ$ photoproduction is less than 200 fb with 0.1 $<$ $ξ$ $<$ 0.5, but can reach about 1.37(1.27) pb with 0.0015 $<$ $ξ$ $<$ 0.5 ( 0.0015 $<$ $ξ$ $<$ 0.15 ). The double $J/ψ$ photoproductio…
We present predictions for the rapidity-differential cross sections of exclusive $Υ$ photoproduction in ultraperipheral collisions (UPCs) of lead ions at the Large Hadron Collider (LHC). We work in the framework of collinear factorization at next-to-leading order (NLO) in perturbative QCD, modeling the generalized parton distributions (GPDs) through the Shuvaev transform of nuclear parton distribution functions (nPDFs). While the effects due to the GPD modeling turn out to be small, the direct NLO predictions still carry significant nPDF-originating uncertainties and depend strongly on the cho…
We have developed a model in which the quantum fluctuations of the proton structure are characterised by hot spots, whose number grows with decreasing Bjorken-$x$. Our model reproduces the $F_2(x,Q^2)$ data from HERA at the relevant scale, as well as the exclusive and dissociative $\mathrm{J/}ψ$ photoproduction data from H1 and ALICE. Our model predicts that for $W_{γ\mathrm{p}} \approx 500$ GeV, the dissociative $\mathrm{J/}ψ$ cross section reaches a maximum and then decreases steeply with energy, which is in qualitatively good agreement to a recent observation that the dissociative $\mathrm{…
Rapidity distributions of vector mesons are computed in dipole model proton-lead ultraperipheral collisions(UPCs) at the CERN Larger Hadron Collider(LHC). The dipole model framework is implemented in the calculations of cross sections in the photon-hadron interaction. The bCGC model and Boosted Gaussian wave functions are employed in the scattering amplitude. We obtain predictions of rapidity distributions of $J/ψ$ meson proton-lead ultraperipheral collisions. The predictions give a good descriptions to the experimental data of ALICE. The rapidity distributions of $ϕ$, $ω$ and $ψ(2s)$ mesons i…
Photoproduction of $ρ^0$ mesons in ultraperipheral heavy ion collisions at energies available at the BNL Relativistic Heavy Ion Collider (RHIC) and CERN Large Hadron Collider (LHC)
In this contribution, we study the inclusive and diffractive $η_{c}$ photoproduction in $pp$ and $pPb$ ultra-peripheral collisions (UPC's) at the LHC Run 2 energies. The quarkonium production is studied using nonrelativistic quantum chromodynamics (NRQCD) formalism. We present predictions for rapidity and transverse momentum distributions for the $η_c$ photoproduction and present our estimate for the total cross sections at the Run 2 energies.
By using models based on Regge phenomenology we analyse the coherent photoproduction of charmonium in peripheral heavy-ion collisions at the Large Hadron Collider (LHC). The centrality dependence is investigated and compared to the experimental results for coherent $J/ψ$ production in lead-lead LHC runs at the energies of 2.76 and 5.02 TeV. Theoretical uncertainties and possible limitations of the formalism are also discussed.
We present the first next-to-leading-order (NLO) perturbative QCD (pQCD) study of rapidity-differential cross sections of coherent exclusive photoproduction of $J/ψ$ mesons in heavy-ion ultraperipheral collisions (UPCs) at the LHC, $dσ/dy(\text{Pb} + \text{Pb} \rightarrow \text{Pb} + J/ψ+ \text{Pb})$. For this, we account for the photon-nucleon NLO cross sections at the forward limit, the $t$ dependence using a standard nuclear form factor, and the photon fluxes of the colliding nuclei. Approximating the generalized parton distributions with their forward-limit parton distribution functions (P…
The exclusive $J/Ψ$ and $Υ$ photoproduction in fixed - target collisions at the LHC and $ep(A)$ collisions at the Electron ion collider in China (EicC) is investigated considering different models for the treatment of the vector meson production at low energies, close to the threshold. Results for the total cross sections and associated distributions are presented. We predict a large number of $J/Ψ$ events at the LHC in the rapidity range covered by the LHCb detector. For the EicC, our predictions point out that a detailed analysis of the near threshold $J/Ψ$ and $Υ$ photoproduction is feasibl…
In this paper we investigate the production of pentaquark states in the photon -- proton interactions present in hadronic collisions at the RHIC and LHC. We consider two phenomenological models for the $J/Ψ$ photoproduction that consider the presence of the $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$ resonances in the $s$ -- channel of the $γp \rightarrow J/Ψp$ reaction. The rapidity distribution is estimated for $pA$ collisions at the RHIC and LHC. Predictions for $pPb$, $Pb \, Ar$ and $Pb \,He$ fixed -- target collisions at the LHC are also presented. We demonstrate that the experimental analys…
Photoproduction of vector mesons are computed in dipole model in proton-proton ultraperipheral collisions(UPCs) at the CERN Large Hadron Collider (LHC). The dipole model framework is employed in the calculations of vector mesons production in diffractive processes. Parameters of the bCGC model are refitted with the latest inclusive deep inelastic scattering experimental data. Employing the bCGC model and Boosted Gaussian light-cone wave function for vector mesons, we obtain prediction of rapidity distributions of $J/ψ$ and $ψ(2s)$ mesons in proton-proton ultraperipheral collisions at the LHC. …
We study the photoproduction of exclusive $2π^+2π^-$ mesons in ultra-peripheral heavy-ion collisions at RHIC and LHC energies. Predictions in photon-nucleus interactions are calculated for various resonances at central and forward rapidities. The recent H1 preliminary data are utilized to improve the description of the poorly known $γp \to 4π^\pm p$ process. We present the comparisons of our results to the available STAR data at RHIC, and made predictions for LHC energies.
We compute the cross section of inclusive dijet photoproduction in ultraperipheral Pb-Pb collisions at the LHC using next-to-leading order perturbative QCD. We demonstrate that our theoretical calculations provide a good description of various kinematic distributions measured by the ATLAS collaboration. We find that the calculated dijet photoproduction cross section is sensitive to nuclear modifications of parton distribution functions (PDFs) at the level of 10 to 20%. Hence, this process can be used to reduce uncertainties in the determination of these nuclear PDFs, whose current magnitude is…
We make predictions for cross sections of $ρ$ and $ϕ$ vector meson photoproduction in ultraperipheral Xe-Xe collisions at $\sqrt{s_{NN}}=5.44$ TeV. Analyzing the momentum transfer distribution of $ρ$ mesons in this process, we explore the feasibility of extracting the nuclear density of $^{129}$Xe, which is needed in searches for dark matter with Xenon-based detectors.
We present the first study of rapidity-differential cross sections of coherent exclusive $J/ψ$ photoproduction in heavy-ion ultraperipheral collisions (UPCs) at the LHC, $\text{d}σ(\text{Pb}+\text{Pb}\rightarrow \text{Pb}+J/ψ+\text{Pb})/\text{d}y$, to NLO in collinear factorisation. Taking the generalised parton distributions as their forward limit counterparts, the NLO contributions in the cross sections are quantified and we show that the real part of the amplitude and quark-PDF contributions must not be neglected. We further evaluate the uncertainties arising from the scale-choice at both L…
In this letter we present, for the first time, the results for the photoproduction of massive gauge bosons in proton -- proton, proton -- Lead and Lead -- Lead collisions at the Large Hadron Collider (LHC), High -- Energy LHC (HE -- LHC) and Future Circular Collider (FCC). Predictions for the rapidity distributions and total cross sections are presented. We predict a large number of events in the rapidity range probed by the LHC detectors, which implies that this process can be used to probe the photoproduction of massive gauge bosons as well to perform the search of Beyond Standard Model phys…
The coherent and incoherent $J/Ψ$ photoproduction in $PbPb$ collisions are investigated considering the possible states of nucleon configurations in the nuclear wave function and taking into account of the non - linear corrections to the QCD dynamics. The cross sections and the rapidity and transverse momentum distributions are estimated for the energies of the next run of the LHC, High -- Energy LHC and Future Circular Collider. Our results indicate that a future experimental analysis of these processes will be useful to discriminate between different approaches for the QCD dynamics as well t…
We investigate the theoretical uncertainty on the predictions for the photoproduction of $ρ$ and $J/Ψ$ states in nucleus-nucleus collisions at Run 2 LHC energies using the Color Dipole formalism. The results for rapidity distributions and total cross sections are presented. Moreover, we compare directly the theoretical results to the recent preliminary data from ALICE collaboration on $ρ$ production in $PbPb$ collisions at central rapidity.
We investigate Higgs-radion mixing scenario through single radion photoproduction process $pp\to pγp\to pRqX$ at the LHC where $X$ represents the remnants of one of the initial protons. We consider high luminosity values of $L_{int}=200\;fb^{-1}$, $500\;fb^{-1}$ and $3000\;fb^{-1}$. We obtain bounds on the mixing parameter space by considering $R\to γγ$, $R\to W^+ W^-$ and $R\to ZZ$ decay channels of the radion as the signal. We also perform a similar analysis for a 100 TeV future proton-proton collider and compare its potential with that of LHC.
The inclusive diffractive quarkonium photoproduction in $pp$ and $pA$ collisions is investigated considering the Resolved Pomeron Model to describe the diffractive interaction. We estimate the rapidity and transverse momentum distributions for the $J/Ψ$, $Ψ(2S)$ and $Υ$ photoproduction in hadronic collisions at the LHC and present our estimate for the total cross sections at the Run 2 energies. A comparison with the predictions associated to the exclusive production also is presented. Our results indicate that the inclusive diffractive production is a factor $\gtrsim 10$ smaller than the exclu…
Over the past years the LHC experiments have reported experimental evidences for processes associated to photon-photon and photon-hadron interactions, showing their potential to investigate the production of low- and high-mass systems in exclusive events. In the particular case of the photoproduction of vector mesons, the experimental study of this final state is expected to shed light on the description of the QCD dynamics at small values of the Bjorken-$x$ variable. In this paper we extend previous studies for the exclusive $J/Ψ$ and $Υ$ photoproduction in $pp$ collisions based on the nonlin…
