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M. Strikman

Publications and source records attributed to M. Strikman.

At least 19 recordsLinked to original sources
arXiv2025

Probing fluctuating protons using forward neutrons in soft and hard inelastic proton-nucleus scattering

We present a model for the distribution of the number of forward neutrons emitted in soft (minimum bias) and hard inelastic proton-nucleus ($pA$) scattering at the LHC. It is based on the Gribov-Glauber model for the distribution over the number of inelastic collisions (wounded nucleons) combined with a parametrization of cross section (color) fluctuations in the projectile proton, which depend on the parton momentum fraction $x_p$, and the assumption of independent neutron emissions. We observe that while the effect of soft color fluctuations is modest, a reduction of the interaction strength with increasing $x_p$ provides the dominant effect. It allows us to qualitatively describe the trend of the ATLAS data on the ZDC energy spectra of forward neutrons emitted in dijet production in inelastic $pA$ scattering at $\sqrt{s_{NN}}=8.16$ TeV.

hep-ph↗
arXiv2025

Physics with high-luminosity proton-nucleus collisions at the LHC

The physics case for the operation of high-luminosity proton-nucleus ($pA$) collisions during Run 3 and 4 at the LHC is reviewed. The collection of $\mathcal{O}$(1-10 pb$^{-1}$) of proton-lead ($p$Pb) collisions at the LHC will provide unique physics opportunities in a broad range of topics including proton and nuclear parton distribution functions (PDFs and nPDFs), generalised parton distributions (GPDs), transverse momentum dependent PDFs (TMDs), low-$x$ QCD and parton saturation, hadron spectroscopy, baseline studies for quark-gluon plasma and parton collectivity, double and triple parton scatterings (DPS/TPS), photon-photon collisions, and physics beyond the Standard Model (BSM); which are not otherwise as clearly accessible by exploiting data from any other colliding system at the LHC. This report summarises the accelerator aspects of high-luminosity $pA$ operation at the LHC, as well as each of the physics topics outlined above, including the relevant experimental measurements that motivate -- much -- larger $pA$ datasets.

hep-ph↗
arXiv2024

Nuclear suppression of coherent $J/ψ$ photoproduction in heavy-ion UPCs and leading twist nuclear shadowing

We determine the nuclear suppression factor $S_{Pb}(x)$, where $x=M_{J/ψ}^2/W_{γp}^2$ with $M_{J/ψ}$ the $J/ψ$ mass and $W_{γp}$ the photon-nucleon energy, for the cross section of coherent $J/ψ$ photoproduction in heavy-ion ultraperipheral collisions (UPCs) at the Large Hadron Collider (LHC) and Relativistic Heavy Ion Collider (RHIC) by performing the $χ^2$ fit to all available data on the cross section $dσ^{AA \to J/ψAA}/dy$ as a function of the $J/ψ$ rapidity $y$ and the photoproduction cross section $σ^{γA \to J/ψA}(W_{γp})$ as a function of $W_{γp}$. We find that while the $dσ^{AA \to J/ψAA}/dy$ data alone constrain $S_{Pb}(x)$ for $x \geq 10^{-3}$, the combined $dσ^{AA \to J/ψAA}/dy$ and $σ^{γA \to J/ψA}(W_{γp})$ data allow us to determine $S_{Pb}(x)$ in the wide interval $10^{-5} < x < 0.05$. In particular, the data favor $S_{Pb}(x)$, which decreases with a decrease of $x$ in the $10^{-4} < x < 0.01$ interval, and can be both decreasing or constant for $x< 10^{-4}$. Identifying $S_{Pb}(x)$ with the ratio of the gluon distributions in Pb and the proton $R_g(x,Q_0^2)=g_A(x,Q_0^2)/[A g_p(x,Q_0^2)]$, we demonstrate that the leading twist approximation (LTA) for nuclear shadowing provides a good description of all the data on $dσ^{AA \to J/ψAA}/dy$ and $σ^{γA \to J/ψA}(W_{γp})$ as well as on the experimental values for $S_{Pb}(x)$ derived from $σ^{γA \to J/ψA}(W_{γp})$. We also show that modern nuclear PDFs reasonably reproduce $S_{Pb}(x)$ as well.

hep-ph↗
arXiv2024

Suppression of diffraction in deep-inelastic scattering on nuclei and dynamical mechanism of leading twist nuclear shadowing

Using the leading twist approach (LTA) to nuclear shadowing, we calculate the ratios of diffractive and usual parton distributions for a heavy nucleus (Pb) and the proton, $R_{A/p}=(f_{i/A}^{D(3)}/f_{i/A})/(f_{i/p}^{D(3)}/f_{i/p})$, for coherent and summed (coherent plus quasi-elastic) nuclear deep-inelastic scattering. We find that $R_{A/p} \approx 0.5-1$ for quarks as well as for the ratio of the diffractive and total cross sections $[(dσ_{\rm diff}/dM_X^2)/σ_{\rm tot}]_{eA}/[(dσ_{\rm diff}/dM_X^2)/σ_{\rm tot}]_{ep}$ and $R_{A/p} \approx 0.5-1.3$ for gluons in a broad range of $x$, including the kinematics of the Electron-Ion Collider, which reaffirms the difference from the nuclear enhancement of $R_{A/p}$ predicted in the gluon saturation framework. We demonstrate that the magnitude of $R_{A/p}$ is controlled by the cross section of the interaction of hadronic fluctuations of the virtual photon with target nucleons, which explains an enhancement of $R_{A/p}$ in the color dipole model and its suppression in LTA. We argue that the black disk limit corresponds to $R_{A/p}=1$ and $R^{\rm coh}_{A/p}=0.86$ for the summed and coherent scattering, respectively. Relying on an intuitive definition of the saturation scale, we show that the ratio of the saturation scales of a heavy nucleus and proton $Q_{sA}^2(b)/Q_{sp}^2(b) \approx 1$ at small impact parameters $b$ due to the strong leading twist nuclear shadowing and diluteness of the nuclear density.

hep-ph↗
arXiv2024

Slicing Pomerons in ultraperipheral collisions using forward neutrons from nuclear breakup

We argue that measurements of forward neutrons from nuclear breakup in inclusive high energy photon-nucleus ($γA$) scattering provide a novel way to study small-$x$ dynamics of QCD in heavy-ion ultraperipheral collisions (UPCs). Using models for hadronic fluctuations of the real photon and neutron emission in nuclear fragmentation, we calculate the distribution over the number of evaporation neutrons produced in $γPb$ collisions at the LHC. We show that it is correlated with the number of wounded nucleons (inelastic collisions) and, hence, can constrain the mechanism of nuclear shadowing and its $x$ dependence.

hep-ph↗
arXiv2024

Electromagnetic Form Factors for Nucleons in Short-Range Correlations and the EMC effect

The relationship between medium modifications of nucleon electromagnetic form factors and nucleon structure functions is examined using a model motivated by Light-Front Holographic QCD (LFHQCD). These modifications are closely connected with the influence of short-ranged correlations. The size of the modifications to nucleon form factors is shown to be about the same as the modifications to the structure functions. Thus, small limits on form factors modifications do not rule out an explanation of the EMC effect motivated by the influence of short range correlations, as claimed by a recent paper.

nucl-th↗
arXiv2024

A=3 (e,e') $x_B \geq 1$ cross-section ratios and the isospin structure of short-range correlations

We study the relation between measured high-$x_B$, high-$Q^2$, Helium-3 to Tritium, $(e,e')$ inclusive-scattering cross-section ratios and the relative abundance of high-momentum neutron-proton ($np$) and proton-proton ($pp$) short-range correlated (SRC) nucleon pairs in three-body ($A=3$) nuclei. Analysis of this data using a simple pair-counting cross-section model suggested a much smaller $np/pp$ ratio than previously measured in heavier nuclei, questioning our understanding of $A=3$ nuclei and, by extension, all other nuclei. Here we examine this finding using spectral-function-based cross-section calculations, with both an \textit{ab initio} $A=3$ spectral function and effective Generalized Contact Formalism (GCF) spectral functions using different nucleon-nucleon interaction models. The \textit{ab initio} calculation agrees with the data, showing good understanding of the structure of $A=3$ nuclei. An 8\% uncertainty on the simple pair-counting model, as implied by the difference between it and the \textit{ab initio} calculation, gives a factor of 5 uncertainty in the extracted $np/pp$ ratio. Thus we see no evidence for the claimed ``unexpected structure in the high-momentum wavefunction for hydrogen-3 and helium-3''.

nucl-th↗
arXiv2023

Photoproduction of $J/ψ$ with neutron tagging in ultra-peripheral collisions of nuclei at RHIC and the LHC

We present predictions for the cross sections of the coherent and incoherent $J/ψ$ photoproduction in ultra-peripheral collisions at RHIC and at the LHC calculated for different classes of events depending on the presence of neutrons emitted by colliding nuclei. Since strong nucleus-nucleus interactions in UPCs are suppressed, it is usually assumed that neutrons at forward rapidities originate mainly from the electromagnetic dissociation of colliding nuclei caused by additional photon exchanges. This is a reasonable assumption for the coherent photoproduction where the state of the target nucleus remains intact. We consider additional sources of neutrons in the incoherent quasielastic and nucleon dissociative $J/ψ$ photoproduction and show that these processes significantly change probabilities of neutron emission compared to calculations when only neutrons from electromagnetic dissociation of nuclei are considered. Such studies should allow one to explore the dynamics of nuclear shadowing in the incoherent $J/ψ$ photoproduction down to $x \sim 10^{-5}$.

hep-ph↗
arXiv2022

Photoproduction of $J/ψ$ in d+Au ultraperipheral collisions at the BNL Relativistic Heavy Ion Collider

We argue that the STAR data on $J/ψ$ photoproduction in $d+Au$ ultraperipheral collisions (UPCs) at the momentum transfer $t \neq 0$ primarily probes elastic and possibly nucleon-dissociative $J/ψ$ photoproduction on quasi-free nucleons, while being essentially insensitive to expectedly weak nuclear modifications of the gluon distribution in the deuteron. Analyzing the STAR detector capabilities for selection of UPC events, we explore the possibility that the contribution of nucleon-dissociative $J/ψ$ photoproduction is negligibly small and obtain a very good description of the $t$ dependence of the STAR total cross section.

hep-ph↗
arXiv2022

Hot Spot model of Nucleon and Double Parton Scattering

We calculate the rate of double parton scattering (DPS) in proton - proton collisions in the framework of the recently proposed hot spot model of the nucleon structure. The resulting rate, especially for the case of three hot spots, appears to be in tension with the current experimental data on DPS at the LHC.

hep-ph↗
arXiv2022

Coherent $J/ ψ$ electroproduction on $^4$He and $^3$He at the Electron-Ion Collider: probing nuclear shadowing one nucleon at a time

While the phenomenon of gluon nuclear shadowing at small $x$ has been getting confirmation in QCD analyses of various LHC measurements involving heavy nuclei, it has not been possible so far to establish experimentally the number of target nucleons responsible for nuclear shadowing in a given process. To address this issue, we study coherent $J / ψ$ electroproduction on $^4$He and $^3$He in the kinematics of a future electron-ion collider and show that this process has the power to disentangle the contributions of the interaction with a specific number of nucleons $k$, in particular, with two nucleons at the momentum transfer $t \neq 0$. We predict a dramatic shift of the $t$-dependence of the differential cross section toward smaller values of $|t|$ due to a non-trivial correlation between $x$ and $k$. This calculation, which makes use for the first time of realistic wave functions, provides a stringent test of models of nuclear shadowing and a novel probe of the 3D imaging of gluons in light nuclei. In addition, thanks to this analysis, unique information on the real part of the corresponding scattering amplitude could be accessed.

hep-ph↗
arXiv2022

Precision QCD, Hadronic Structure & Forward QCD, Heavy Ions: Report of Energy Frontier Topical Groups 5, 6, 7 submitted to Snowmass 2021

This report was prepared on behalf of three Energy Frontier Topical Groups of the Snowmass 2021 Community Planning Exercise. It summarizes the status and implications of studies of strong interactions in high-energy experiments and QCD theory. We emphasize the rich landscape and broad impact of these studies in the decade ahead. Hadronic interactions play a central role in the high-luminosity Large Hadron Collider (LHC) physics program, and strong synergies exist between the (HL-)LHC and planned or proposed experiments at the U.S. Electron-Ion Collider, CERN forward physics experiments, high-intensity facilities, and future TeV-range lepton and hadron colliders. Prospects for precision determinations of the strong coupling and a variety of nonperturbative distribution and fragmentation functions are examined. We also review the potential of envisioned tests of new dynamical regimes of QCD in high-energy and high-density scattering processes with nucleon, ion, and photon initial states. The important role of the high-energy heavy-ion program in studies of nuclear structure and the nuclear medium, and its connections with QCD involving nucleons are summarized. We address ongoing and future theoretical advancements in multi-loop QCD computations, lattice QCD, jet substructure, and event generators. Cross-cutting connections between experimental measurements, theoretical predictions, large-scale data analysis, and high-performance computing are emphasized.

hep-ph↗
arXiv2022

UPC contribution to forward rapidity gap distribution in pPb collisions at the LHC

In this Letter, we consider strong and electromagnetic (ultraperipheral) mechanisms in proton-nucleus coherent diffraction at the CERN Large Hadron Collider. We explicitly demonstrate the dominance of the latter and explain the CMS data on the forward rapidity gap distribution in $pPb$ collisions at $\sqrt{s_{NN}}=8.16$ TeV. In particular, we provide simple estimates, which give a good, semi-quantitative description of both magnitude and shape of the $Δη^F$ distribution in the Pomeron-proton topology. We also make predictions for the proton-oxygen run.

hep-ph↗
arXiv2022

Selected topics in diffraction with protons and nuclei: past, present, and future

We review a broad range of phenomena in diffraction in the context of hadron-hadron, hadron-nucleus collisions and deep inelastic lepton-proton/nucleus scattering focusing on the interplay between the perturbative QCD and non-perturbative models. We discuss inclusive diffraction in DIS, phenomenology of dipole models, resummation and parton saturation at low $x$, hard diffractive production of vector mesons, inelastic diffraction in hadron-hadron scattering, formalism of color fluctuations, inclusive coherent and incoherent diffraction as well as soft and hard diffraction phenomena in hadron-hadron/nucleus and photon-nucleus collisions. For each topic we review key results from the past and present experiments including HERA and the LHC. Finally, we identify the remaining open questions, which could be addressed in the continuing experiments, in particular in photon-induced reactions at the LHC and the future Electron-Ion Collider (EIC) in the US, Large Hadron electron Collider (LHeC) and Future Circular Collider (FCC) at CERN.

hep-ph↗
arXiv2021

Nucleon off-shell structure and the free neutron valence structure from A=3 inclusive electron scattering measurements

Understanding the differences between the distribution of quarks bound in protons and neutrons is key for constraining the mechanisms of SU(6) spin-flavor symmetry breaking in Quantum Chromodynamics (QCD). While vast amounts of proton structure measurements were done, data on the structure of the neutron is much more spars as experiments typically extract the structure of neutrons from measurements of light atomic nuclei using model-dependent corrections for nuclear effects. Recently the MARATHON collaboration performed such an extraction by measuring inclusive deep-inelastic electron-scattering on helium-3 and tritium mirror nuclei where nuclear effects are expected to be similar and thus be suppressed in the helium-3 to tritium ratio. Here we evaluate the model dependence of this extraction by examining a wide range of models including the effect of using instant-form and light-cone nuclear wave functions and several different parameterizations of nucleon modification effects, including those with and without isospin dependence. We find that, while the data cannot differentiate among the different models of nuclear structure and nucleon modification, they consistently prefer a neutron-to-proton structure function ratio of at $x_B \rightarrow 1$ of $\sim 0.4$ with a typical uncertainty ($1σ$) of $\sim0.05$ and $\sim0.10$ for isospin-independent and isospin-dependent modification models, respectively. While strongly favoring SU(6) symmetry breaking models based on perturbative QCD and the Schwinger-Dyson equation calculation, the MARATHON data do not completely rule out the scalar di-quark models if an isospin-dependent modification exist.

hep-ph↗
arXiv2021

Nuclear suppression from coherent $J/ψ$ photoproduction at the Large Hadron Collider

Using the data on coherent $J/ψ$ photoproduction in Pb-Pb ultraperipheral collisions (UPCs) obtained in Runs 1 and 2 at the Large Hadron Collider (LHC), we determined with a good accuracy the nuclear suppression factor of $S_{Pb}(x)$ in a wide range of the momentum fraction $x$, $10^{-5} \leq x \leq 0.04$. In the small-$x$ region $x < 10^{-3}$, our $χ^2$ fit favors a flat form of $S_{Pb}(x) \approx 0.6$ with approximately a 5% accuracy for $x=6 \times 10^{-4} - 10^{-3} $ and a 25% error at $x=10^{-4}$. At the same time, uncertainties of the fit do not exclude a slow decrease of $S_{Pb}(x)$ in the small-$x$ limit. At large $x$, $S_{Pb}(x)$ is constrained to better than 10% precision up to $x=0.04$ and is also consistent with the value of $S_{Pb}(x)$ at $\langle x \rangle =0.042$, which we extract from the Fermilab data on the $A$ dependence of the cross section of coherent $J/ψ$ photoproduction on fixed nuclear targets. The resulting uncertainties on $S_{Pb}(x)$ are small, which indicates the potential of the LHC data on coherent charmonium photoproduction in Pb-Pb UPCs to provide additional constraints on small-$x$ nPDFs. We explicitly demonstrate this using as an example the EPPS16 and nCTEQ16 nuclear parton distribution functions, whose uncertainties decrease severalfold after the Bayesian reweighting of the discussed UPC data.

hep-ph↗
arXiv2021

Possible studies at the first stage of the NICA collider operation with polarized and unpolarized proton and deuteron beams

This paper contains suggestions for experiments with usage of the Spin Physics Detector (SPD) at the first stage of the SPD NICA Programme developing at JINR. Double polarized pp-, dd- and pd- collisions at c.m.s. NN energies of 3.4-10 GeV, which will be accessible at the initial stage of experiments, allow one to study spin dependence of the NN interaction, search for multiquark states at double strangeness, charm and beauty thresholds, study the short-range structure of the deuteron. Double polarized pd scattering offer a possibility to test the Standard Model through the search for T-invariance violation.

hep-ph↗