How well can we predict the total cross section at the LHC?
P V Landshoff
不依赖于任何理论，CDF声称的Tevatron截面的大值是正确的可能性表明，LHC的总截面可能很大。由于实验和理论的不确定性，最佳预测值为$125\pm 35$ mb。
Independently of any theory, the possibility that the large value of the Tevatron cross section claimed by CDF is correct suggests that the total cross section at the LHC may be large. Because of the experimental and theoretical uncertainities, the best prediction is $125\pm 35$ mb.
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We suggest that, if current measurements of inclusive jet production for central rapidities at the LHC are extended to lower transverse momenta, one could define a visible cross section sensitive to the unitarity bound set by the recent determination of the inelastic proton-proton cross section.
We describe the most recent results at the Large Hadron Collider from the ALICE, ATLAS, CMS, LHCb and TOTEM experiments concerning the elastic, inelastic and total cross section measurements as well as particle production in soft and hard processes.
Within the leading logarithmic approximation of perturbative QCD and the leading twist approach to nuclear shadowing, we compare the cross sections of photoproduction of $J/ψ$ and $ψ(2S)$ mesons on nuclei in Pb-Pb UPCs in the LHC kinematics. We find that the nuclear suppression of these cross sections due to the nuclear gluon shadowing is large and rather similar in the $J/ψ$ and $ψ(2S)$ cases.
We study the precision with which the t-channel single top quark production cross section is expected to be measured in future LHC runs at 14 TeV. The single top final state has a lepton and neutrino from the top quark decay plus two jets, one of which is required to be b-tagged. This measurement is done in the context of the Snowmass 2013 study for the low-luminosity 14 TeV and the high-luminosity 14 TeV LHC as well as for high-luminosity 33 TeV LHC.
We study the possibilities to analyse the data on leading neutrons production at first LHC runs. These data could be used to extract from it $π^+ p$ and $π^+π^+$ cross-sections. In this note we estimate relative contributions of $π$, $ρ$ and $a_2$ reggeons to charge exchanges and discuss related problems of measurements.
The total cross section at the LHC
由于有效的QCD耦合并不小，所以我们不能用微扰理论来精确计算长程强相互作用效应。尽管如此，我还是表明我们知道很多，尽管还远远不够。作为我们知识缺乏的一个衡量标准，在LHC能量下对总截面的最佳预测是125 +/- 25 mb。
Recent experimental data on elastic scattering of high energy protons show that the critical regime has been reached at LHC energies. The approach to criticality is demonstrated by increase of the ratio of elastic to total cross sections from ISR to LHC energies. At LHC it reaches the value which can result in principal change of the character of proton interactions. The treatment of new physics of hollowed toroid-like hadrons requires usage of another branch of the unitarity condition. Its further fate is speculated and interpreted with the help of the unitarity condition in combination with …
We present the inclusive Higgs boson cross-section at the LHC with collision energy of 8 TeV. Our predictions are obtained using our publicly available program iHixs which incorporates NNLO QCD corrections and electroweak corrections. We review the convergence of the QCD perturbative expansion at this new energy and examine the impact of finite Higgs width effects. We also study the impact of different parton distribution functions on the cross-section. We present tables with the cross-section values and estimates for their uncertainty due to uncalculated higher orders in the perturbative expa…
The staged increase of the LHC beam energy provides a new class of interesting observables, namely ratios and double ratios of cross sections of various hard processes. The large degree of correlation of theoretical systematics in the cross section calculations at different energies leads to highly precise predictions for such ratios. We present in this letter few examples of such ratios, and discuss their possible implications, both in terms of opportunities for precision measurements and in terms of sensitivity to Beyond the Standard Model dynamics.
Results from the large hadron collider (LHC) show that no available Monte Carlo simulation incorporates our pre-LHC knowledge of soft and hard diffraction in a way that could be reliably extrapolated to LHC energies. As a simulation is needed to establish triggers, perform underlying event corrections and calculate acceptances, the lack of a robust simulation affects all measurements at the LHC. Particularly affected are the measurements of processes with large diffractive rapidity gaps, which constitute about one quarter of the inelastic cross section. In this paper, a previously described ph…
In this talk, we present a way to improve the accuracy of theoretical predictions for Higgs boson production cross sections at the LHC using the measurements of lepton angular distributions. In this regards, we exploit the sensitivity of the lepton angular coefficient associated with the longitudinal Z-boson polarization to the parton density function (PDF) for gluons resolved from the incoming protons, in order to constrain the Higgs boson cross section from gluon fusion processes. We find that high-statistics determinations of the longitudinally polarized angular coefficient at the LHC Run 3…
We compare predictions for the W, Z, gg->H and t-tbar total cross sections at the Large Hadron Collider (LHC), for a centre-of-mass energy of 7 TeV, using the most recent publicly available next-to-leading order and next-to-next-to-leading order parton distribution functions (PDFs) from all PDF fitting groups. In particular, we focus on the dependence on the different values of the strong coupling, alpha_S(M_Z^2), used by each group. We also perform a comparison of the relevant quark-antiquark and gluon-gluon luminosity functions. We make some comments on the recent PDF4LHC recommendations. Fi…
We present theoretical predictions for the Higgs boson production cross-section via gluon fusion at the LHC in a Standard Model with four generations. We include QCD corrections through NLO retaining the full dependence on the quark masses, and the NNLO corrections in the heavy quark effective theory approximation. We also include electroweak corrections through three loops. Electroweak and bottom-quark contributions are suppressed in comparison to the Standard Model with three generations.
The total cross section at the LHC
硬坡密子最初是在深度非弹性轻子散射中被发现的，但它似乎服从类似于其他Regge交换的因式分解，这一事实加强了它对软强子碰撞也有贡献的证据。在对sigma（pp）和sigma（\bar p）数据的拟合中包括硬坡密子项会导致LHC的大的总截面。由于筛选校正产生的不确定性，不可能进行精确预测;最佳估计值为125 \pm 25 mb。
The impact of recent measurements of heavy-flavour production in deep inelastic $ep$ scattering and in $pp$ collisions on parton distribution functions is studied in a QCD analysis in the fixed-flavour number scheme at next-to-leading order. Differential cross sections of charm- and beauty-hadron production measured by LHCb are used together with inclusive and heavy-flavour production cross sections in deep inelastic scattering at HERA. The heavy-flavour data of the LHCb experiment impose additional constraints on the gluon and the sea-quark distributions at low partonic fractions $x$ of the p…
In this note we give interim recommendations on how to evaluate LHC cross sections for (neutral) Higgs production and Higgs branching ratios in the general (CP-conserving) Two-Higgs-Doublet Model (2HDM). The current status of available higher-order corrections to Higgs production and decay in this model is discussed, and the existing public codes implementing these calculations are described. Numerical results are presented for a set of reference scenarios, demonstrating the very good agreement between the results obtained using different programs.
The Large Hadron Collider experiments are probing the evolution of the strong coupling $α_s$ up to the TeV scale. We show how the ratio of 3- to 2-jets cross sections is affected by the presence of new physics and argue that it can be used to place a model-independent bound on new particles carrying QCD color charge. The current data potentially constrains such states to be heavier than a few hundred GeVs.
Analysis of $dσ/dt$ of the TOTEM Collaboration data, carried out without model assumptions, showed the existence of a new effect in the behavior of the hadron scattering amplitude at a small momentum transfer at a high confidence level. The quantitatively description of the data in the framework of the HEGS model support such phenomenon which can be connect with quark potentials at large distances.
We consider QCD radiative corrections to the production of four charged leptons in the ZZ signal region at the LHC. We report on the complete calculation of the next-to-next-to-leading order (NNLO) corrections to this process in QCD perturbation theory. Numerical results are presented for $\sqrt{s}=8$ TeV, using typical selection cuts applied by the ATLAS and CMS collaborations. The NNLO corrections increase the NLO fiducial cross section by about $15\%$, and they have a relatively small impact on the shape of the considered kinematical distributions. In the case of the $ΔΦ$ distribution of th…
We present an updated study of the systematic errors in the measurements of the electroweak boson cross-sections at the LHC for various experimental cuts for a center of mass energy of 7, 10 and 14 TeV. The size of both electroweak and NNLO QCD contributions are estimated, together with the systematic error from the parton distributions. The effects of new versions of the MSTW, CTEQ, and NNPDF PDFs are considered.
Higgs production through gluon fusion: updated cross sections at the Tevatron and the LHC
我们提出了强子碰撞中胶子-胶子融合产生希格斯玻色子的总截面的最新预测。我们的计算包括目前最先进的理论信息，可观察到：软胶子重混到下一个到下一个到领先的对数精度，下一个到领先的顺序，和双回路电弱效应的底夸克贡献的确切治疗。我们采用最新的参数化部分子分布函数在次-领先的顺序，我们评估相应的不确定性。与我们以前的中心预测相比，在Tevatron上，差异范围从m_H=115 GeV的+9%到m_H=200 GeV的-9%。在大型强子对撞机上，截面反而显著增加。这种效应从115 GeV的+30%增加到300 GeV的+9%，主要是由于新的部分子分布函数.我们还为LHC在sqrt{s}=10 TeV处提供了新的预测。
Constraining the SMEFT with a differential cross section measurement of $tWZ$ production at the HL-LHC
本研究前瞻性地在HL-LHC上测量tWZ产生过程的微分截面，构建SMEFT参数模型以约束威尔逊系数，虽约束弱于相关测量，但可为全局SMEFT分析提供独特输入。
Total, elastic and diffractive cross sections at LHC in the Miettinen-Pumplin model
在Miettinen-Pumplin模型的框架下，对LHC的总截面、弹性截面和单衍射截面进行了预测。总截面比Donnachie和Landshoff在软坡密子模型中确定的小15%。衍射截面在Tevatron-LHC能量范围内几乎是恒定的。
We propose a measurement of leading neutrons spectra at LHC in order to extract inclusive $π^+ p$ and $π^+π^+$ cross-sections with high $p_T$ jets production. The cross-sections for these processes are simulated with the use of parton distributions in hadrons. In this work we estimate the possibility to extract parton distributions in the pion from the data on these cross-sections and also search for signatures of fundamental differences in the pion and proton structure.
We present predictions for the inclusive cross section for Higgs boson production by gluon--gluon fusion in proton collisions at $\sqrt{s}=8$ TeV. Our calculation is accurate up to next-to-next-to-leading order in QCD perturbation theory and includes soft-gluon effects up to next-to-next-to-leading logarithmic accuracy and two-loop electroweak corrections. The dependence on heavy-quark masses is taken into account exactly up to next-to-leading order and next-to-leading logarithmic accuracy, and a treatment of the Higgs boson line-shape is provided according to the complex-pole scheme.
It is expected that the LHC will soon discover the Higgs boson, or that failure to find it will severely constrain its production cross-section over a large mass range. Either one of these results spells trouble for a fourth generation that significantly enhances the Higgs production cross-section at LHC. In fact the LHC has already ruled out a SM Higgs mass in the range of 120 GeV to 600 GeV with a fourth generation at the 95% C.L. In this paper we explore options within extended scalar sectors to maintain the viability of a heavy fourth generation if an enhanced (relative to the Standard Mod…
Standard Model $ZZ$ production is an important background for many searches at the LHC, especially in final states with missing transverse momentum. In this article, boson substitution is applied to estimate $ZZ \rightarrow \ell^+ \ell^- ν\barν$ yields from $Zγ\rightarrow \ell^+ \ell^- γ$ events. The cross-section ratio of the two processes and its uncertainties are evaluated at NNLO with the MATRIX generator as a function of the transverse momentum of the substituted boson. Uncertainties due to higher-order QCD corrections, parton distribution functions, photon isolation criteria, and electro…
Elastic proton-proton scattering is reviewed starting from the results of the LHC experiments conducted by the TOTEM and ATLAS collaborations, and the HEGS model and a simple phenomenological parametrisation are compared with the new data on the differential elastic proton-proton scattering cross section, which detect a non-exponential behaviour of the differential cross sections in the first diffraction cone. We consider the influence of various assumptions on the extraction of the elastic scattering parameters, and on the deduction of the total cross section.
Heavy colored scalar particles, which exist in many models of new physics, can be pair produced at the Large Hadron Collider (LHC) via gluon-gluon fusion and possibly form quarkonium-like bound states. If the scalars are also charged under the electroweak gauge group, these bound states can then decay into electroweak bosons. This yields a resonant cross section for final states such as gamma gamma that can exceed Standard Model backgrounds. This paper studies this process in the Manohar-Wise model of color-octet scalars (COS). Important threshold logarithms and final state Coulomb-like QCD in…
This is a short communication with a summary of results obtained with a model based on Gribov's reggeon calculus, which was proposed and applied to processes of soft diffraction at high energies. We present a brief description of the model and its predictions for various LHC energies.
We calculate the leading order cross section for the associated production of Z and J/ψ. Processes that include associated production of electroweak bosons and heavy quarlonium can give valuable insight to the production mechanism of quarkonia. We conclude that this process is accessible by the LHC statistics.
We discuss expectations for the total and inelastic cross-sections at LHC CM energies $\sqrt{s}\ =\ 7\ TeV$ {and $ 14\ TeV$} obtained in an eikonal minijet model augmented by soft gluon $k_t$-resummation, which we describe in some detail. We present a band of predictions which encompass recent LHC data and suggest that the inelastic cross-section described by two channel eikonal models include only uncorrelated processes. We show that this interpretation of the model is supported by the LHC data.
A model based on Gribov's Regge calculus was developed [1] and was proposed to describe diffractive processes. In this note we present numerical vales obtained from [1] for the dependence of single diffraction cross-section on diffractive mass at $\sqrt{s}$ = 0.9, 2.76 and 7 TeV.
Total Cross-Sections : Cross-Talk between HERA, LHC and LC
我们讨论了需要比较总截面测量在LHC和HERA彼此和可用的模型，以获得更精确的预测在未来的线性对撞机的总强子截面，从而导致更好的估计强子背景。
We respond to some criticism questioning the validity of the current Standard Model Higgs exclusion limits at the Tevatron, due to the significant dependence of the dominant production cross section from gluon-gluon fusion on the choice of parton distribution functions (PDFs) and the strong coupling (alpha_S). We demonstrate the ability of the Tevatron jet data to discriminate between different high-x gluon distributions, performing a detailed quantitative comparison to show that fits not explicitly including these data fail to give a good description. In this context we emphasise the importan…
Prospects for b-quark production cross section measurements in pp collisions at the LHC
对大型强子对撞机上$b$ -夸克产生测量的理论和实验方面的简要回顾。
Motivated by the observation of the first hidden charm pentaquarks by the LHCb collaboration in 2015 and the updated analysis with an order-of-magnitude larger data set in 2019, we estimate their cross sections for the prompt production as well as their heavy quark spin partners, in the $Σ_c^{(*)}\bar{D}^{(*)}$ hadronic molecular picture, at the center-of-mass energy $7~\mathrm{TeV}$ in the $pp$ collision. Their cross sections are several $\mathrm{nb}$ and we would expect several tens hidden charm pentaquark events in the LHC based on its current integrated luminosity. The cross sections show …
A proposal for an experiment to measure the cross section of antiproton production in a proton-nuclear collision in a kinematically forbidden region for nucleon-nucleon interaction on a fixed LHC target is considered. It is shown that this process can be separated from the kinematically allowed production process using the existing detectors of the ALICE facility at a proton energy of 7 TeV with a fixed nuclear target. Assuming the scale dependence of the cross section, the data obtained can be used to estimate the subthreshold cross section for the production of superheavy particles with a ma…
Photon bremsstrahlung is proposed to be used to identify elastic proton-proton interactions at the LHC. In addition to a measurement of the elastic pp cross section (assuming that the elastic slope is known), the bremsstrahlung photons will allow the evaluation of the total pp cross section, luminosity and to align the Zero Degree Calorimeters (ZDCs).
A fundamental characteristic of hadron colliders is the abundant production of jets, which then are studied to learn about hard QCD, the proton structure, or nonperturbative effects. In the following the latest results and developments from the LHC experiments on jet cross sections, event shapes, flavour and rapidity dependence, and cross section ratios are presented. The ratio of the inclusive 3-jet to the inclusive 2-jet event cross section is used for a first determination of the strong coupling constant at the TeV scale.
The parton distribution functions (PDFs) are a non-negotiable input to almost all theory predictions at hadron colliders. In this talk, I introduce PDF determination by global analysis and discuss selected topics concerning recent relevant data from HERA and the Tevatron, before giving some prospects for the LHC. The combination of H1 and ZEUS cross sections reduces uncertainties and will be an important input to future global PDF analyses. The theoretical description of the heavy-quark contribution to structure functions at HERA has a significant influence on predictions at the LHC. New W and…
Total cross-section at LHC from minijets and soft gluon resummation in the infrared region
本文描述了一个包含QCD喷流截面和软胶子再活化的总截面模型，并与目前的$pp$和${\bar p}p$截面数据进行了比较。预测LHC提出了不同的参数集。它示出，它们不同，根据可用的部分子密度函数的小x-行为。
SM and MSSM Higgs Boson Production Cross Sections at the Tevatron and the LHC
我们目前的SM和MSSM希格斯玻色子生产的截面在Tevatron和LHC的结果。SM截面是最先进的理论预测的汇编。MSSM的截面获得的SM的通过有效的耦合近似，在FeynHiggs实现。数值结果已经获得了在四个基准场景的两个值的tan β，tan β = 5，40。
A Regge pole model for Pomeron-Pomeron total cross section in the resonance region $\sqrt{M^2}\le$ 5 GeV is presented. The cross section is saturated by direct-channel contributions from the Pomeron as well as from two different $f$ trajectories, accompanied by the isolated f$_0(500)$ resonance which dominates the $\sqrt{M^{2}}\lesssim 1$ GeV region. A slowly varying background is taken into account. The calculated Pomeron-Pomeron total cross section cannot be measured directly, but is an essential part of central diffractive processes. In preparation of future calculations of central resonanc…
I review the predictions of the total cross section for many models, and point out that some of them lead to the conclusion that the standard experimental analysis may lead to systematic errors much larger than expected.
Universal properties of elastic pp cross section from the ISR to the LHC
本研究探究从ISR到LHC能区弹性微分pp截面峰谷位之比恒定的唯象学，验证几何标度在LHC的适用性，并分析其对ρ参数和峰谷截面值比的影响。
We study the determination of supersymmetric parameters at the LHC from a global fit including cross sections and edges of kinematic distributions. For illustration, we focus on a minimal supergravity scenario and discuss how well it can be constrained at the LHC operating at 7 and 14 TeV collision energy, respectively. We find that the inclusion of cross sections greatly improves the accuracy of the SUSY parameter determination, and allows to reliably extract model parameters even in the initial phase of LHC data taking with 7 TeV collision energy and 1/fb integrated luminosity. Moreover, cro…
In this paper we study the photon production in single and double diffractive processes considering the Resolved Pomeron model. We estimate the rapidity and transverse momentum dependence of the cross section for the diffractive double photon and photon+jet production. A comparison with the inclusive production is presented. We predict large values for the total cross sections, which makes the experimental analysis of these observables feasible at LHC energies.
We review the status of NNLO calculations for jet cross sections at the LHC. In particular, we describe how perturbative stability and convergence can be used as criteria to select the most appropriate scales in the theoretical description of di-jet and single jet inclusive production.
How precisely will the total cross section be measured at the LHC?
强子散射很有可能在大型强子对撞机上进入一个新的领域，因为达到了黑盘极限。这将导致弹性散射振幅的实部和斜率的t依赖性的严重变化，并且这又可能使总截面的测量产生偏差。我们研究这个问题，并提出新的策略来测试总截面测量的可靠性。
I present the latest calculations of total and differential cross sections for top-antitop pair production and single top quark production via all main partonic channels. Higher-order corrections from the resummation of soft gluons are added through NNLL accuracy. Detailed numerical results are presented for approximate NNLO cross sections and top quark transverse momentum distributions at the Tevatron and LHC colliders.
The total $W$-boson decay width $Γ_W$ is an important observable which allows testing of the standard model. The current world average value is based on direct measurements of final state kinematic properties of $W$-boson decays, and has a relative uncertainty of 2%. The indirect determination of $Γ_W$ via the cross-section measurements of vector-boson production can lead to a similar accuracy. The same methodology leads also to a determination of the leptonic branching ratio. This approach has been successfully pursued by the CDF and D0 experiments at the Tevatron collider, as well as by the …
We carry out a comprehensive analysis of models for top A_{FB} at CDF in light of new top data arriving from the LHC. We begin with a careful Tevatron analysis, considering in general which sets of effective vertices give rise to a large forward-backward asymmetry while suppressing the contribution to the total t tbar cross-section. We show on general grounds that scalar models struggle to produce sufficient asymmetries consistent with CDF observations, while vector models can produce a large asymmetry with a less significant tension in the total cross-section and $t\bar{t}$ invariant mass dis…
Simple generic expressions to compute double-parton scattering (DPS) cross sections in high-energy proton-nucleus and nucleus-nucleus collisions, as a function of the corresponding single-parton cross sections, are presented. Estimates of DPS contributions are studied for two specific processes at LHC energies: (i) same-sign W-boson pair production in p-Pb, and (ii) double-J/psi production in Pb-Pb, using NLO predictions with nuclear parton densities for the corresponding single-parton cross sections. The expected DPS cross sections and event rates after typical acceptance and efficiency losse…
To settle the question whether the growth with energy is universal for different hadronic total cross-sections, we present results from theoretical models for pion-proton, proton-proton and proton-antiproton total cross-sections. We show that present and planned experiments at LHC can differentiate between different models, all of which are consistent with presently available (lower energy) data. This study is also relevant for the analysis of those very high energy cosmic ray data which require reliable pion-proton total cross-sections as seeds. A preliminary study of the total pion-pion cros…
Using nonrelativistic QCD (NRQCD) factorization, we calculate the yields for $J/ψ$, $ψ(2S)$ and $Υ(1S)$ hadroproduction at $\sqrt{s}=$ 72 GeV and 115 GeV including the next-to-leading order QCD corrections. Both these center-of-mass energies correspond to those obtained with 7~TeV and 2.76~TeV nucleon beam impinging a fixed target. We study the cross section integrated in $p_t$ as a function of the rapidity as well as the $p_t$ differential cross section in the central rapidity region. Using different NLO fit results of the NRQCD long-distance matrix elements, we evaluate a theoretical uncerta…
In the light of the latest data by LHCf collaboration of the LHC on leading neutrons spectra it is possible to obtain total pion-proton cross-sections in the TeV energy region. In this work the exact extraction procedure is shown. Final numbers for the pion-proton cross-section are collected at several different values of the colliding energy and compared with some popular theoretical predictions. Errors of results are estimated.
We present an estimate of survival probability from an eikonal mini- jet model implemented with a proposal for soft gluon resummation to all orders. We compare it with experimental data for diffractive di-jet production from LHC experiments, CMS and ATLAS, both at LO and NLO order.
Photoinduced inclusive cross sections in hadronic collisions at the LHC
本文研究了LHC上pp与pA散射中的包容性电磁解离过程，提出利用虚光子交换和深度非弹性结构函数计算相关截面，并指出pA→XA反应可测量极高能下质子的总光吸收截面。
We consider the ratio between the double and single Higgs production cross sections and examine the prospect of measuring the trilinear Higgs self-coupling using this observable. Such a ratio has a reduced theoretical (scale) uncertainty than the double Higgs cross section. We find that with 600/fb, the 14 TeV LHC can constraint the trilinear Higgs self coupling to be positive, and with 3000/fb one could measure it with a +30 % {-20 %}) accuracy.
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