arXiv subjects

V. A. Khoze

Publications and source records attributed to V. A. Khoze.

At least 19 recordsLinked to original sources

arXiv2026

Odderon in the diffractive dip region

We examine possible $C$-odd effects in elastic proton-proton and proton-antiproton scattering in the diffractive dip region. Collider data with $\sqrt{s}>500$ GeV are fitted for $0.2<|t|<1~\GeV^2$, using a simple Regge-inspired parametrization of effective $C$-even and $C$-odd amplitudes. The relative phases are not left free, but are fixed by the signature factors of the corresponding even and odd contributions. In this way, the real and imaginary parts of each term are linked by crossing. The $C$-even amplitude is first described by three effective Pomeron-like terms. The $C$-odd sector is then tested with several one-term Odderon-like forms. We find that the fits do not require a stable nonzero $C$-odd term: the odd contribution is either compatible with zero or becomes weakly constrained when we allow extra freedom. We then test whether the conclusion is changed by adding either a fourth Pomeron-like term or a second Odderon-like term. The improvement obtained with the fourth Pomeron-like term is mainly $C$-even, while the second Odderon-like term is not resolved as an independent contribution. These results provide a complementary test of recent determinations of the Odderon amplitude based on scaling and analyticity.

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arXiv2026

Odderon exchange in high-energy $K^0_S$ regeneration at the LHC

We revisit the possibility of detecting the Odderon exchange through high-energy neutral-kaon regeneration, focusing on the in-matter $K^0_L\to K^0_S$ conversion of $(\sim\!0.2-2)$~TeV $K^0_L$ mesons originating from $pp$ collisions at $\sqrt{s}=13.6$~TeV, and on the practical constraints of realizing such a measurement in the very-forward region of an LHC interaction point. The analysis has two complementary parts. First, we reproduce the original coherent-forward-regeneration estimates for a liquid-hydrogen regenerator and extend them to realistic C, Cu and Pb regenerators of an LHC-compatible geometry, including neutral-kaon attenuation. We show that an Odderon-induced regeneration phase produces a measurable distortion of the $K^0\toπ^0π^0$ decay-vertex distribution at TeV kaon energies, but that the survival of primary $K^0_S$ mesons from the interaction point imposes severe baseline requirements, while a competing electromagnetic $C=-1$ (photon-exchange) amplitude limits the interpretation of the coherent mode as a clean Odderon measurement. Second, we examine non-forward (diffractive) regeneration at lower kaon energies of $0.2-0.8$~TeV, where the primary-$K^0_S$ contamination is naturally suppressed, and estimate the competing Odderon, Pomeron--Odderon-cut, $ω$-Reggeon and photon-exchange contributions to the regeneration amplitude. We identify neutron-induced neutral-only strangeness production and inelastic Regge backgrounds as the dominant limitations, quantify the background suppression required for an observable Odderon signal, and formulate the ingredients of an active double-regenerator subtraction strategy.

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arXiv2026

Hunting for QCD Instantons

Instantons are non-perturbative classical solutions which describe transitions between different QCD vacua. They have never been observed experimentally. We consider the signatures of the instanton (sphaleron) production events and the main QCD backgrounds. The possibilities to search for the QCD instantons in the diffractive (i.e. with a large rapidity gap) events at the LHC and via the spin-spin correlations between two hyperons at NICA are discussed.

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arXiv2024

Odderon in the light of collider low-$t$ data

Odderon is the $C$-odd amplitude that does not fall (or decrease very slowly) with energy. The expected amplitude is small and mainly real. Therefore, extracting it from the data on top of a much larger $C$-even contribution is challenging. The only chance is to consider the very low $|t|$ region of Coulomb nuclear interference or the diffractive dip region. Here we perform the analysis of elastic scattering $pp$ and $\bar pp$ data at low momentum transfer $|t| < 0.1$ GeV$^2$ within large collider energy interval $\sqrt s = 50$ GeV $-$ 13 TeV in order to evaluate quantitatively the possible Odderon contribution. We use the two-channel eikonal model, which naturally accounts for the screening of the Odderon amplitude by the $C$-even (Pomeron) exchanges.

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arXiv2024

Odderon contribution in light of the LHC low-$t$ data

We perform the analysis of elastic scattering $pp$ and $\bar{p}p$ data at low momentum transfer $|t|<0.1$ GeV$^2$ within large collider energy interval $\sqrt{s}=50$ GeV - 13 TeV in order to evaluate quantitatively the possible Odderon contribution. We use the two-channel eikonal model, which naturally accounts for the screening of the Odderon amplitude by $C$-even (Pomeron) exchanges.

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arXiv2024

The Low soft-photon theorem again

It is shown that contrary to claims of Ref. [1] the formulated in the proper physical variables Low theorem [2] for soft photon emission does not require any modification. We also reject the criticism in Ref. [1] of the papers [3,4]. At the same time, we identify some inaccuracies in Ref. [3] in the presentation of the soft-photon theorem for the case of spin-one-half particles. We also point out shortcomings in consideration of the Low theorem in the classic textbooks [5,6].

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arXiv2023

Large Rapidity Gaps in proton-nucleus interaction

We analyse the cross-section of events with Large Rapidity Gaps observed in proton-lead collisions by the CMS collaboration. The role of the transverse size of elementary $pN$ amplitude is discussed. We emphasize that the cross-section of incoming proton dissociation caused by the photon radiated off the lead ion is close to the value of $dσ/dΔη^F$ measured by the CMS, and it is not clear why there is no room in the data for the Pomeron-induced contribution

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arXiv2023

Searches for QCD instantons with forward proton tagging

We study the possibility to observe heavy ($M_{\rm inst}> 60$ GeV) QCD instantons at the LHC in events with one or two tagged leading protons including fast simulation of detector and pile-up effects. We show that the expected instanton signal in a single-tagged configuration is strongly affected by central detector and pile-up effects. For double-tagged approach, where larger integrated luminosities and hence larger pile-up contaminations need to be considered, the combinatorial background overwhelms the expected signal. We suggest that additional time information about tracks at central and forward rapidities would be crucial for potential improvements.

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arXiv2022

Central Instanton Production

We study the central production of QCD instantons at hadron colliders in events with two large rapidity gaps. These gaps in rapidity are formed by either Pomeron or photon exchanges or a combination of the two. The kT-factorization formalism is used to reduce the factorization scale dependence. We compute for the first time the relevant differential cross-sections for a complete set of central instanton production processes at the LHC, including gluon-induced and quark-induced amplitudes, and also show that the largest contribution comes from processes with Pomeron exchanges where a single gluon from each Pomeron couples to the instanton.

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arXiv2021

A new approach to modelling elastic and inelastic photon-initiated production at the LHC: SuperChic 4

We present the results of the new SuperChic 4 Monte Carlo implementation of photon-initiated production in proton-proton collisions, considering as a first example the case of lepton pair production. This is based on the structure function calculation of the underlying process, and focusses on a complete account of the various contributing channels, including the case where a rapidity gap veto is imposed. We provide a careful treatment of the contributions where either (single dissociation), both (double dissociation) or neither (elastic) proton interacts inelastically and dissociates, and interface our results to Pythia for showering and hadronization. The particle decay distribution from dissociation system, as well the survival probability for no additional proton-proton interactions, are both fully accounted for; these are essential for comparing to data where a rapidity gap veto is applied. We present detailed results for the impact of the veto requirement on the differential cross section, compare to and find good agreement with ATLAS 7 TeV data on semi-exclusive production, and provide a new precise evaluation of the background from semi-exclusive lepton pair production to SUSY particle production in compressed mass scenarios, which is found to be low.

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arXiv2021

Elastic photon-initiated production at the LHC: the role of hadron-hadron interactions

We analyse in detail the role of additional hadron-hadron interactions in elastic photon-initiated (PI) production at the LHC, both in $pp$ and heavy ion collisions. We first demonstrate that the source of difference between our predictions and other results in the literature for PI muon pair production is dominantly due to an unphysical cut that is imposed in these latter results on the dimuon-hadron impact parameter. We in addition show that this is experimentally disfavoured by the shape of the muon kinematic distributions measured by ATLAS in ultraperipheral PbPb collisions. We then consider the theoretical uncertainty due to the survival probability for no additional hadron-hadron interactions, and in particular the role this may play in the tendency for the predicted cross sections to lie somewhat above ATLAS data on PI muon pair production, in both $pp$ and PbPb collisions. This difference is relatively mild, at the $\sim 10\%$ level, and hence a very good control over the theory is clearly required. We show that this uncertainty is very small, and it is only by taking very extreme and rather unphysical variations in the modelling of the survival factor that this tension can be removed. This underlines the basic, rather model independent, point that a significant fraction of elastic PI scattering occurs for hadron-hadron impact parameters that are simply outside the range of QCD interactions, and hence this sets a lower bound on the survival factor in any physically reasonable approach. Finally, other possible origins for this discrepancy are discussed.

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arXiv2021

Hunting for QCD Instantons at the LHC in Events with Large Rapidity Gaps

We outline a strategy of how to search for QCD instantons of invariant mass 20 -- 60 GeV in diffractive events in low luminosity runs at the LHC. We show that by imposing appropriate selection criteria on the final states, one can select the kinematic regime where the instanton signal exceeds the background by a factor of at least 8. In spite of the relatively strong cuts that we impose on the total transverse energy and the number of charged tracks, $\sum_i E_{T,i}>15$ GeV, $N_{\rm ch}>20$ measured within the $0<η<2$ interval and excluding events with high $p_{T}$ particles, the expected cross-section is sufficiently large to study the instanton production in the events with Large Rapidity Gaps at low luminosities, thus avoiding problems with pile-up. The paper also includes an updated computation of instanton cross-sections and other parameters relevant for the ongoing studies.

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arXiv2020

Dynamics of diffractive dissociation

We describe a QCD based model which incorporates the main properties of the inclusive particle distributions expected for diffractive processes, including the diffractive dissociation at high energies. We study, in turn, the total cross section, $σ_{tot}$, the differential elastic, $dσ_{el}/dt$, cross section, the dependence of the single proton dissociation cross section, $ξd^{SD}/dξ$, on the momentum fraction, $ξ= 1-x_L$, lost by the leading proton, the multiplicity distributions in inelastic (non-diffractive) collisions and in the processes of dissociation. Besides this we calculate the mean transverse momenta of the `wee partons' (secondaries) produced in the case of dissociation (that is in the processes with a large rapidity gap) and compare it with that in inelastic interactions.

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arXiv2020

Isolating the Odderon in central production in high energy $pA$ and $AA$ collisions

We study the rapidity dependence of the cross section on the rapidity of the central exclusive production cross sections of C-even mesons in $pA$ and $AA$ collisions, where $A$ is a heavy ion. We observe qualitatively different behaviour of the contributions arising from $γ$-Odderon and Pomeron-Pomeron fusion mechanisms. This can be used to extract the Odderon signal from the events of $f_2$ mesons exclusively produced in the forward region. Estimates, obtained using expected values of the Odderon cross section, indicate that the $γ$-Odderon contribution may exceed by a few times the Pomeron-induced background in Pb-Pb collisions. Moreover, the Odderon effect can be clearly seen in terms of the asymmetry in $pA$ and $AA$ collisions with the beam and target reversed. It is particularly interesting to note that the asymmetry for $γ$-Odderon fusion reaches its maximum value close to 1 in the forward direction, whereas the asymmetry for the Pomeron-Pomeron fusion contribution is small. The role of additional interactions of the $f_2$ meson with nucleons in the heavy ion, and also the contributions from secondary Reggeons, are estimated. The photon-Odderon contribution has a large normalisation uncertainty but the enhances cross-section in the forward region combined with a large asymmetry increases the chance of experimentally detecting the Odderon.

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arXiv2020

Bethe phase including proton excitations

We evaluate the contribution of inelastic intermediate states (such as $p\to N^*$ excitations) to the phase between the one-photon-exchange and the `nuclear' high energy $pp$ scattering amplitudes as $t\to 0$, caused by multiphoton diagrams. It turns out to be rather small - much smaller than to have any influence on the experimental accuracy of the measurements of $ρ$, defined to be the ratio of the real to imaginary parts of the forward `nuclear' amplitude.

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arXiv2019

Searches for Dark Matter at the LHC in forward proton mode

We analyze in detail the LHC prospects at the center-of-mass energy of 14 TeV for charged electroweakino searches, decaying to leptons, in compressed supersymmetry scenarios, via exclusive photon-initiated pair production. This provides a potentially increased sensitivity in comparison to inclusive channels, where the background is often overwhelming. We pay particular attention to the challenges that such searches would face in the hostile high pile-up environment of the LHC, giving close consideration to the backgrounds that will be present. The signal we focus on is the exclusive production of same-flavour muon and electron pairs, with missing energy in the final state, and with two outgoing intact protons registered by the dedicated forward proton detectors installed in association with ATLAS and CMS. We present results for slepton masses of 120--300 GeV and slepton-neutralino mass splitting of 10-20 GeV, and find that the relevant backgrounds can be controlled to the level of the expected signal yields. The most significant such backgrounds are due to semi-exclusive lepton pair production at lower masses, with a proton produced in the initial proton dissociation system registering in the forward detectors, and from the coincidence of forward protons produced in pile-up events with an inclusive central event that mimics the signal. We also outline a range of potential methods to further suppress these backgrounds as well as to enlarge the signal yields.

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arXiv2019

Colliding Pomerons

We recall the main properties of inclusive particle distributions expected for Pomeron-proton and Pomeron-Pomeron interactions. Due to the small size of the Pomeron we expect larger transverse momenta of secondaries and a smaller probability of Multiple Interactions, that is a narrower multiplicity distribution. We propose to compare the spectra of secondaries produced in the Pomeron and the proton interactions in terms of the Feynman $x_F$ variable. The main difference should be observed for a relatively large $x_F$, that is near the edge of rapidity gaps. Such data offer the opportunity to illuminate the properties of the `soft' or `Regge' Pomeron, which drives the minimum-bias type of events in high energy $pp$ interactions. Besides this, there should be a good opportunity to observe a glueball in the Pomeron fragmentation region.

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arXiv2019

The fusion of hard and soft Pomerons: 3-jet diffractive production

We consider the central exclusive production of high $E_T$ jets $pp\to p+(X+{\rm dijet})+p$. In particular we study the possible contamination of the purely exclusive signal by semi-exclusive production where no other secondaries are emitted in one hemisphere, between the highest $E_T$ dijet and the recoil proton, while in the other hemisphere a third jet, plus possibly additional hadron activity, is allowed, but still separated from the incoming proton by a large rapidity gap. This process arising from the fusion of a hard and a soft Pomeron has not been considered before. It turns out that it gives a negligible contribution. %contamination, which was not known before the calculation. The calculation involves a careful treatment of the QCD colour structure of the amplitudes.

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