Detection of two-photon exclusive production of supersymmetric pairs at the LHC
N. Schul, K. Piotrzkowski
备注：
9 pages, 5 tables, 8 figures. Talk given at the Workshop on "High-energy photon collisions at the LHC", April 22-25, 2008, CERN, Switzerland. To appear in the proceedings
The detection of pairs of sleptons, charginos and charged higgs bosons produced via photon-photon fusion at the LHC is studied, assuming a couple of benchmark points of the MSSM model. Due to low cross sections, it requires large integrated luminosity, but thanks to the striking signature of these exclusive processes the backgrounds are low, and are well known. Very forward proton detectors can be used to measure the photon energies, allowing for direct determination of masses of the lightest SUSY particle, of selectrons and smuons with a few GeV resolution. Finally, the detection and mass measurement of quasi-stable particles predicted by the so-called sweet spot supersymmetry is discussed.
In this report, we describe the most recent results on exclusive diffraction from the ATLAS, CMS, LHCb, TOTEM experiments at the LHC concerning exclusive pions, $J/Ψ$, $Ψ(2S)$, dilepton, diphoton, $WW$ productions and prospects concerning the search for anomalous couplings and axion-like particle production.
In this contribution we report on the investigations of the exclusive production of J/psi and psi(2S) states in proton-proton and nucleus-nucleus reactions at the LHC using the theoretical framework of light-cone dipole formalism.
The cross section for exclusive psi(2S) ultraperipheral production at the LHC is calculated using gluon parametrisations extracted from exclusive J/psi measurements performed at HERA and the LHC. Predictions are given at leading and next-to-leading order for pp centre-of-mass energies of 7, 8 and 14 TeV, assuming the non-relativistic approximation for the psi(2S) wave function.
The implementation of exclusive diffractive production of Higgs boson and dijets in the FPMC (Forward Physics Monte Carlo) framework is presented following the models by Khoze, Martin, Ryskin and Cudell, Dechambre, Hernandez and Ivanov. The predictions of the models are compared to the CDF measurement of exclusive jets and the uncertainties on the Higgs boson and jet production cross sections at the LHC are discussed.
The feasibility studies of the central exclusive jet production at the LHC using the proton tagging technique are presented. Three classes of data taking scenarios are considered: double tag at high pile-up, single tag at low pile-up and double tag at low pile-up. Analyses were performed at the c.m. energy of 14 TeV for the ATLAS experiment, but are also valid for the CMS/TOTEM detectors.
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.
Central exclusive production at hadron colliders is characterised by the hadronic state produced at or close to midrapidity, and by the two forward scattered protons, or remnants thereof. No particles are produced between the midrapidity system and the forward going beam particles, and such events can hence be identified experimentally by a double-gap topology. At LHC energies, central exclusive production in proton-proton collisions is dominated by pomeron-pomeron fusion. The models to describe such reactions are reviewed, and the ongoing efforts in the ALICE Collaboration to analyse double-g…
In this paper we present a detailed analysis of the contribution of the Light -- by -- Light (LbL), Durham and double diffractive processes for the diphoton production in ultraperipheral $PbPb$ collisions at the Large Hadron Collider (LHC), High -- Energy LHC (HE -- LHC) and Future Circular Collider (FCC). The acceptance of the central and forward LHC detectors is taken into account and predictions for the invariant mass, rapidity, transverse momentum and acoplanarity distributions are presented. Our results indicate that the contribution of the Durham and double diffractive processes can be s…
We present the recent measurements of exclusive processes performed in the CMS experiment at the LHC using data collected at a centre of mass energy of 7 TeV. These measurements include the double-pomeron production of photon pairs, the two-photon production of leptons pairs, and the previously undetected two-photon production of W boson pairs. While in case of the two first processes that enables to set limits on production cross-section, in the later case it provides also stringent limits on the anomalous quartic gauge couplings.
The production of a quarkonium -- pair in exclusive and diffractive processes in $pp$ collisions at the LHC and FCC energies is investigated. We consider the $J/ΨJ/Ψ$ and $ΥΥ$ production in these processes and present predictions for the transverse momentum and rapidity distributions considering the kinematical ranges expected to be covered by central and forward detectors. Results for the cross sections are also presented. Our results indicate that the double $J/Ψ$ production is dominated by the exclusive process, while the double $Υ$ production receive a large contribution of the diffractive…
In this contribution we summarize recent results on the computation of cross sections for glueball candidates production in quasi-real photon-photon collisions and on central diffraction processes, i.e. double Pomeron exchange, in heavy ion interactions at the LHC are computed. In particular, we provide predictions for the production of exotic mesons f0(1500), f0(1710) and X(1835). The rates for these distinct production channels are compared.
The feasibility studies of the measurement of the central exclusive jet production at the LHC using the proton tagging technique are presented. In order to reach the low jet-mass region, single tagged events were considered. The studies were performed at the c.m. energy of 14 TeV and the ATLAS detector, but are also applicable for the CMS-TOTEM experiments. Four data-taking scenarios were considered: AFP and ALFA detectors as forward proton taggers and $β^*$ = 0.55 m and $β^*$ = 90 m optics. After the event selection, the signal-to-background ratio ranges between 5 and $10^4$. Finally, the exp…
We investigate the prospects for Central Exclusive Diffractive (CED) production of MSSM Higgs bosons at the LHC using forward proton detectors (FPD) proposed to be installed 220 m and 420 m from ATLAS and CMS detectors. We summarize the situation after the first and very successful data taking period of the LHC. The discovery of a Higgs boson and results from searches for additional MSSM Higgs bosons from the ATLAS and CMS, have recently led to a proposal of new low-energy MSSM benchmark scenarios. The CED signal cross section for the process H -> bb and its backgrounds are estimated in these …
We focus on exclusive production of neutral technipion $\tilde π^0$ in $pp$ collisions at the LHC, i.e. on $p p \to p p \tilde π^0$ reaction. The dependence of the cross section on parameters of recently proposed vector-like Technicolor model is studied. Characteristic features of the differential distributions are discussed. For not too large technipion masses the diphoton decay channel has the dominant branching fraction. This is also the main reason for an enhanced production of neutral technipions in $γγ$-fusion reaction. We discuss potential backgrounds of the QCD and QED origin to the $p…
We resum a class of large Sudakov logarithms affecting Higgs boson production in the exclusive one-jet bin at the LHC. We extend previous results by calculating the full one-loop soft function for this process, which extends the accuracy of the resummation to include the leading three logarithmic corrections at each order in the QCD coupling constant. We match this result to the next-to-leading order cross section and present a detailed numerical study assuming realistic LHC cuts. Careful attention is paid to the matching procedure, and to the theoretical uncertainties induced by residual scal…
Using the framework of collinear factorization in perturbative QCD (pQCD), we analyze the recent data of the LHCb and ALICE collaborations on exclusive photoproduction of J/ψ in ultraperipheral pp and AA collisions, respectively. We demonstrate that the simultaneous analysis of the proton and Pb data allows us to reduce the ambiguity of the pQCD description of the $γp \to J/ψp$ and $γA \to J/ψp$ cross sections and, hence, to place additional constraints on the gluon distributions in the nucleon and nuclei at small x. We also make predictions for the cross section of coherent exclusive photopro…
A process of Central Exclusive $π^+π^-$ production in proton-proton collisions and its theoretical description is presented. A possibility of its measurement, during the special low luminosity LHC runs, with the help of the ATLAS central detector for measuring pions and the ALFA stations for tagging the scattered protons is studied. A visible cross section is estimated to be 21 $μ$b for $\sqrt{s}=7$ TeV, which gives over 2000 events for 100 $μ$b$^{-1}$ of integrated luminosity. Differential distributions in pion pseudorapidities, pion and proton transverse momenta as well as $π^+π^-$ invariant…
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…
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.
In this work we investigate the exclusive photoproduction of J/psi and the radially excited psi(2S) state off nucleon in proton-proton collisions. The theoretical framework considered in the analysis is the light-cone dipole formalism and predictions are done for proton-proton collisions at the CERN-LHC energy of 7 TeV. The theoretical uncertainties are investigated and comparison is done to the recent LHCb Collaboration data for the exclusive charmonium production.
Two theoretical descriptions of exclusive diffractive jets and Higgs production at the LHC were implemented into the FPMC generator: the Khoze, Martin, Ryskin model and the Cudell, Hernández, Ivanov, Dechambre exclusive model. We then study the uncertainties. We compare their predictions to the CDF measurement and discuss the possibility of constraining the exclusive Higgs production at the LHC with early measurements of exclusive jets. We show that the present theoretical uncertainties can be reduced with such data by a factor of 5.
On February 6, 2019, an EMMI workshop on 'Central exclusive production at the LHC' was held at Heidelberg. Here we make some remarks on the topics presented in the talks and the discussions of this meeting. We hope that this will be useful for further studies of central exclusive reactions.
The current uncertainty on the gluon density extracted from the global parton analysis is large in the kinematical range of small values of the Bjorken - $x$ variable and low values of the hard scale $Q^2$. An alternative to reduces this uncertainty is the analysis of the exclusive vector meson photoproduction in photon - hadron and hadron - hadron collisions. This process offers a unique opportunity to constrain the gluon density of the proton, since its cross section is proportional to the gluon density squared. In this paper we consider current parametrizations for the gluon distribution an…
It is well know that the precise measurement of $H\toγγ$ can generate two degenerate parameter spaces of $Hγγ$ anomalous coupling. We propose to utilize the exclusive Higgs rare decays $H\toΥ(ns)+γ$ to break above mentioned degeneracy and further to constrain the $Hγγ$ anomalous coupling at the HL-LHC. We demonstrate that the branching ratios of $H\toΥ(ns)+γ$ can be significantly enhanced in the non-SM-like parameter space from $H\toγγ$ measurement, due to the destructive interference between the direct and indirect production of $Υ(ns)$ in the SM. By applying the NRQCD factorization formalism…
Particle production in two-photon interactions at hadronic collisions is becoming increasingly relevant in the LHC physics programme as a way to improve our understanding of the Standard Model and search for signals of New Physics. A key ingredient for the study of these interactions in $pp$ collisions is the description of the photon content of the proton, which allow us to derive predictions for the cross sections associated to events where occur the proton dissociation (non - exclusive processes) and for those where both incident protons remain intact (exclusive processes). In this paper, a…
In the Randall-Sundrum (RS) scenario the compactification radius of the extra dimension is stabilized by the radion, which is a scalar field lighter than the graviton Kaluza-Klein states. It implies that the detection of the radion will be the first signature of the stabilized RS model. In this paper we study the exclusive production of the radion in electromagnetic and diffractive hadron - hadron collisions at the LHC. Our results demonstrate that the diffractive production of radion is dominant and should be feasible of study at CERN LHC.
In this paper we estimate the production of dimuons ($μ^+ μ^-$) in exclusive photon -- photon ($γγ$) and diffractive Pomeron - Pomeron $(I\!P I\!P)$, Pomeron - Reggeon $(I\!P I\!R)$ and Reggeon - Reggeon $(I\!R I\!R)$ interactions in $pp$ collisions at the LHC energy. The invariant mass, rapidity and tranverse momentum distributions are calculated using the Forward Physics Monte Carlo (FPMC), which allows to obtain realistic predictions for the dimuon production with two leading intact hadrons. In particular, predictions taking into account the CMS and LHCb acceptances are presented. Moreover,…
In this paper we perform a systematic study of the exclusive dilepton production by $γγ$ interactions in $PbPb$ collisions at the LHC Run 2 energies considering different levels of precision for the treatment of the absorptive corrections and for the nuclear form factor. The rapidity and invariant mass distributions are estimated taking into account the experimental cutoffs and a comparison with the recent ALICE and ATLAS data for the $e^+ e^-$ and $μ^+ μ^-$ production is presented.
Heavy nuclei at collider energies are a source of high energy Weizsaecker-Williams photons. This photon flux may be utilized to study high energy photon-nucleus interactions. Here we concentrate on the coherent diffractive production of heavy vector mesons on nuclear targets and show how it probes the unintegrated glue of the nucleus in the saturation domain. We present predictions for rapidity distributions of exclusive coherent J/Psi and Upsilon mesons which can be measured by the ALICE experiment at the LHC.
At forward rapidities and high energies we expect to probe the non-linear regime of Quantum Chromodynamics (QCD). One of the most promising observables to constrain the QCD dynamics in this regime is exclusive vector meson photoproduction (EVMP). We study the EVMP in association with a leading baryon (product of the proton dissociation) in photon-hadron interactions that take place in $pp$ and $p$Pb collisions at large impact parameters. We present the rapidity distributions for $ρ$ and $J/ψ$ photoproduction in association with a leading baryon (neutron and delta states) at LHC run 2 energies.…
The dilepton production in diffractive and exclusive processes at forward rapidities considering ultraperipheral $PbPb$ collisions at the LHC is investigated. Predictions for the $e^+ e^-$, $μ^+ μ^-$ and $τ^+ τ^-$ cross sections are presented taking into account of realistic cuts that can be implemented by the LHCb Collaboration in a future experimental analysis. Our results indicate that the background associated with the diffractive production can be strongly suppressed and the exclusive processes can be cleanly separated. For the $τ^+ τ^-$ production, the semi and purely leptonic decay chan…
We present results of the updated SuperChic 3 Monte Carlo event generator for central exclusive production. This extends the previous treatment of proton-proton collisions to include heavy ion (pA and AA) beams, for both photon and QCD-initiated production, the first time such a unified treatment of exclusive processes has been presented in a single generator. To achieve this we have developed a theory of the gap survival factor in heavy ion collisions, which allows us to derive some straightforward results about the $A$ scaling of the corresponding cross sections. We compare against the recen…
We study the implications at the LHC for the minimal (least) version of the supersymmetric standard model. In this model supersymmetry is broken by gravity and extra gauge interactions effects, providing a spectrum similar in several aspects to that in natural supersymmetric scenarios. Having the first two generations of sparticles partially decoupled means that any significant signal can only involve gauginos and the third family of sfermions. In practice, the signals are dominated by gluino production with subsequent decays into the stop sector. As we show, for gluino masses below 2300 GeV, …
We investigate the LHC discovery potential of R-parity violating supersymmetric models with a right-handed selectron or smuon as the lightest supersymmetric particle (LSP). These LSPs arise naturally in R-parity violating minimal supergravity models. We classify the hadron collider signatures and perform for the first time within these models a detailed signal over background analysis. We develop an inclusive three-lepton search and give prospects for a discovery at a center-of-mass energy of 7 TeV as well as 14 TeV. There are extensive parameter regions which the LHC can already test with 7 T…
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.
The existence of a dilaton as a pseudo-Nambu-Goldstone boson in spontaneous breaking of scale symmetry is predicted in beyond standard model theories in which electroweak symmetry is broken via strongly coupled conformal dynamics. Such a particle is expected to have a mass below the conformal symmetry breaking scale $f$ and couplings to standard model particles similar to those of the SM Higgs boson. In this paper we estimate, for the first time, the dilaton production in exclusive processes considering Pomeron - Pomeron ($\pom \pom$) and photon - photon ($γγ$) interactions, which are characte…
The exclusive $Υ$ photoproduction in proton-proton and proton - nucleus collisions at LHC energies is investigated using the color dipole formalism and considering different models for the $Υ$ wave function and forward dipole - target scattering amplitude. Our goal is to update the color dipole predictions and estimate the theoretical uncertainty present in these predictions. We present predictions for the kinematical ranges probed by the ALICE, CMS and LHCb Collaborations.
Low-$x$ parton densities accounting for absorptive effects and exclusive $J/ψ$ and $Υ$ data from the LHC
IRFU, CEA, Université Paris-Saclay（巴黎萨克雷大学）；Centre for Cosmology, Particle Physics and Phenomenology (CP3), Université Catholique de Louvain（鲁汶天主教大学）；Institute for Particle Physics Phenomenology, Durham University（杜伦大学）；NRC Kurchatov Institute, PNPI（库尔恰托夫研究所）
We study the potential of the exclusive $pp\to p\ell^-\ell^+p$ process to probe excited leptons at the LHC which is known to be one of the most clean channel at the hadron colliders. The sensitivity of the model parameters is obtained 95% confidence level by considering three forward detector acceptances; $0.0015< ξ< 0.5$, $0.0015< ξ<0.15$ and $0.1< ξ< 0.5$.
The recent LHCb data for exclusive $J/ψ$ peripheral production at 13 TeV motivate an improved `NLO' analysis to estimate the gluon distribution at low $x$ in which we re-calculate the rapidity gap survival factors and use a more precise expression for the photon flux. We comment on the difference between the $k_T$ and collinear factorization approaches.
The type II seesaw model predicts the existence of a doubly charged Higgs boson ($H ^{\pm\pm}$), which can be produced through the Drell - Yan process and photon -- induced interactions at hadronic colliders. In recent years, such reactions have been largely investigated in inclusive processes, where both incident protons breakup and a large number of particles is produced in addition to the doubly charged Higgs pair. In this paper, we investigate, for the first time, the possibility of searching for $H ^{\pm\pm}$ in exclusive processes, which are characterized by two rapidity gaps and two int…
We present a new calculation of axion-like particle (ALP) production in the semi-exclusive photon-initiated (PI) channel, that is either with intact outgoing protons or rapidity gaps present in the final state, and with no colour flow between the colliding LHC protons. This is the first full treatment of this process, accounting for both the possibility of proton dissociation and the survival factor probability of no additional proton-proton interactions, including its kinematic and process dependence. We present the expected event yields in the case that either one or both protons are require…
We study the exclusive production of heavy flavors at central rapidities in hadron-hadron collisions within the kT factorisation formalism. Since this involves regions of small Bjorken x in the unintegrated gluon densities, we include the next-to-leading order BFKL contributions working directly in transverse momentum representation. Our results are presented in a form suitable for Monte Carlo implementation.
We present state-of-the art predictions for the production of supersymmetric squarks and gluinos at the Large Hadron Collider (LHC), including soft-gluon resummation up to next-to-next-to-leading logarithmic (NNLL) accuracy, the resummation of Coulomb corrections and the contribution from bound states. The NNLL corrections enhance the cross-section predictions and reduce the scale uncertainty to a level of 5-10%. The NNLL resummed cross-section predictions can be obtained from the computer code NNLL-fast, which also provides the scale uncertainty and the pdf and alpha_s error.
Vector boson fusion (VBF) processes offer a promising avenue to study the non-colored sectors of supersymmetric extensions of the Standard Model at the LHC. A feasibility study for searching for the chargino/neutralino system in the $R-$parity conserving Minimal Supersymmetric Standard Model is presented. The high $E_T$ forward jets in opposite hemispheres are utilized to trigger VBF events, so that the production of the lightest chargino and the second lightest neutralino can be probed without a bias by experimental triggers. Kinematic requirements are developed to search for signals of these…
In this paper we present a comprehensive analysis of the exclusive heavy quark photoproduction in $pp$, $pPb$ and $PbPb$ collisions at LHC and FCC energies using the color dipole formalism and taking into account of nonlinear corrections to the QCD dynamics. We estimate the rapidity distributions and cross sections for the charm and bottom production considering three phenomenological models for the dipole-proton scattering amplitude that are able to describe the $ep$ HERA data. Our results indicate that a future experimental analysis of this process is feasible, which will allow us to improve…
