Nuclear Theory·nucl-th

Thursday·July 6, 2023

12 papers—5 primary·7 cross-listed

06
Collider constraints on massive gravitons coupling to photons
David d'Enterria (CERN)🇨🇭 · Malak Ait Tamlihat (Mohammed V University in Rabat)🇲🇦 · Laurent Schoeffel (CEA)🇫🇷 · Hua-Sheng Shao (LPTHE)🇫🇷 · Yahya Tayalati (Mohammed V University in Rabat)🇲🇦
We study the discovery potential of massive graviton-like spin-2 particles coupled to standard model fields, produced in photon-photon collisions at the Large Hadron Collider (LHC) as well as in electron-positron ( $e^{+} e^{-}$ ) collisions, within an effective theory with and without universal couplings. Our focus is on a massive graviton G coupled to the electromagnetic field, which decays via $G \to γ γ$ and leads to a resonant excess of diphotons over the light-by-light scattering continuum at the LHC, and of triphoton final states at $e^{+} e^{-}$ colliders. Based on similar searches performed for pseudoscalar axion-like particles (ALPs), and taking into account the different cross sections, $γ γ$ partial widths, and decay kinematics of the pseudoscalar and tensor particles, we reinterpret existing experimental bounds on the ALP- $γ$ coupling into G- $γ$ ones. Using the available data, exclusion limits on the graviton-photon coupling are set down to $g_{G γ γ} \approx 1$ --0.05~TeV $^{- 1}$ for masses $m_{G} \approx 100$ ~MeV--2~TeV. Such bounds can be improved by factors of 100 at Belle~II in the low-mass region, and of 4 at the HL-LHC at high masses, with their expected full integrated luminosities.
↳ hep-phhep-exnucl-exnucl-thPLB(2023)·24 citations
07
Collider physics with no PDFs
Tuomas Lappi🇫🇮 · Heikki Mäntysaari🇫🇮 · Hannu Paukkunen🇫🇮 · Mirja Tevio🇫🇮
Measurements of Deep Inelastic Scattering (DIS) provide a powerful tool to probe the fundamental structure of protons and other nuclei. The DIS cross sections can be expressed in terms of structure functions which are conventionally expressed in terms of parton distribution functions (PDFs) that obey the DGLAP evolution equations. However, it is also possible to formulate the DGLAP evolution directly in terms of measurable DIS structure functions entirely sidestepping the need for introducing PDFs. We call this as the physical-basis approach. In a global analysis one would thereby directly parametrize the (observable) structure functions -- not the (unobservable) PDFs. Ideally, with data constraints at fixed $Q^{2}$ , the initial condition for the evolution would be the same at each perturbative order (unlike for PDFs) and the approach thus provides a more clean test of the QCD dynamics. We first study a physical basis consisting of the structure functions $F_{2}$ and $F_{L}$ in the fixed-flavour number scheme to the leading non-zero order in $α_{s}$ . We show how to express the quark singlet and gluon PDFs in terms of $F_{2}$ and $F_{L}$ directly in momentum space which then leads to the DGLAP evolution of the structure functions $F_{2}$ and $F_{L}$ . In the second step we expand the physical basis to include six independent structure functions, which allows for a consistent global analysis. The steps towards NLO accuracy and the variable-flavour-number scheme are outlined. At NLO accuracy (when the scheme dependence of PDFs starts to play a part), we can take advatage of the physical basis and express e.g. the Drell-Yan cross sections at the LHC directly in terms of measurable DIS structure functions and thus without the scheme dependence.
↳ hep-phnucl-th1 citation
08
Holographic baryons, dense matter and neutron star mergers
Matti Jarvinen🇰🇷
The gauge/gravity duality, combined with information from lattice QCD, nuclear theory, and perturbative QCD, can be used to constrain the equation of state of hot and dense QCD. I discuss an approach based on the holographic V-QCD model. I start by reviewing the results from the construction of the V-QCD baryon as a soliton of the gauge fields in the model. Then I discuss implementing nuclear matter in the model by using a homogeneous approach. The model predicts a strongly first order phase transition from nuclear to quark matter with a critical endpoint. By using the model in state-of-the-art simulations of neutron star binaries with parameters consistent with GW170817, I study the formation of quark matter during the merger process.
↳ hep-phnucl-thJHAP(2023)·4 citations
09
Quantum simulation of in-medium QCD jets: momentum broadening, gluon production, and entropy growth
João Barata🇺🇸 · Xiaojian Du🇪🇸 · Meijian Li🇪🇸 · Wenyang Qian🇪🇸 · Carlos A. Salgado🇪🇸
Jets provide one of the primary probes of the quark-gluon plasma produced in ultrarelativistic heavy ion collisions and the cold nuclear matter explored in deep inelastic scattering experiments. However, despite important developments in the last years, a description of the real-time evolution of QCD jets inside a medium is still far from being complete. In our previous work, we have explored quantum technologies as a promising alternative theoretical laboratory to simulate jet evolution in QCD matter, to overcome inherent technical difficulties in present calculations. Here, we extend our previous investigation from the single particle $∣ q ⟩$ to the $∣ q ⟩ + ∣ q g ⟩$ Fock space, taking into account gluon production. Based on the light-front Hamiltonian formalism, we construct a digital quantum circuit that tracks the evolution of a multi-particle jet probe in the presence of a medium described as a stochastic color field. Studying the momentum broadening of the jet state, we observe sizable sub-eikonal effects by comparing to eikonal estimates. We also study the medium-induced modifications to the gluon emission probability, which exhibit small corrections compared to the vacuum splitting function. In addition, we study the time evolution of the von-Neumann entropy associated with the quark component; we find that the exponential of the entropy grows linearly in time for the bare quark but super-linearly when taking into account gluon emission.
↳ hep-phnucl-thquant-phPRD(2023)·53 citations
10
Long-Lived Particles and the Quiet Sun
R. Andrew Gustafson🇺🇸 · Ryan Plestid🇺🇸 · Ian M. Shoemaker🇺🇸 · Albert Zhou🇩🇪
The nuclear reaction network within the interior of the Sun is an efficient MeV physics factory, and can produce long-lived particles generic to dark sector models. In this work we consider the sensitivity of satellite instruments, primarily the RHESSI Spectrometer, that observe the Quiet Sun in the MeV regime where backgrounds are low. We find that Quiet Sun observations offer a powerful and complementary probe in regions of parameter space where the long-lived particle decay length is longer than the radius of the Sun, and shorter than the distance between the Sun and Earth. We comment on connections to recent model-building work on heavy neutral leptons coupled to neutrinos and high-quality axions from mirror symmetries.
↳ hep-phastro-ph.HEastro-ph.SRnucl-thPRD(2024)·5 citations
11
Femtoscopy of $D$ mesons and light mesons upon unitarized effective field theories
Juan M. Torres-Rincon🇪🇸 · Àngels Ramos🇪🇸 · Laura Tolos🇪🇸
Hadron femtoscopy has turned into a powerful tool for accessing space-time information of heavy-ion collisions as well as for studying final-state interactions of hadrons. Recently, heavy-flavor femtoscopy has become feasible using the ALICE detector at the LHC. We compute the correlation function of $D$ mesons and light mesons using an off-shell $T$ -matrix approach to access the two-meson wave function, and predict the correlation functions involving charged $D^{+}, D^{*+}, D_{s}^{+}$ and $D_{s}^{*+}$ with $π^{\pm}$ and $K^{\pm}$ . From the obtained results -- all of them accessible in $p + p$ collision experiments -- we point up the case of $D^{+} π^{-}$ , which is sensitive to the lower state of the two-pole $D_{0}^{*} (2300)$ system. The presence of such poles imprints a depletion on the correlation function, which could potentially be detected in experiments. While preliminary ALICE data do not show evidence of this effect, we suggest to look into the $D_{s}^{+} K^{-}$ system to explore the higher pole of the $D_{0}^{*} (2300)$ , as the depletion in the correlation function is more pronounced. Using heavy-quark spin symmetry we also propose exploring the effect of the two poles of the $D_{1} (2430)$ and predict similar structures in the correlation functions of the $D^{*+} π^{-}$ and $D_{s}^{*+} K^{-}$ pairs.
↳ hep-phnucl-thPRD(2023)·50 citations
12
X17 discovery potential from $γ D \to e^{+} e^{-} p n$ with neutron tagging
Cornelis J.G. Mommers🇩🇪 · Marc Vanderhaeghen🇩🇪
We propose a novel direct search experiment for X17 using the reaction $γ D \to e^{+} e^{-} p n$ . X17 is a hypothetical particle conjectured by the ATOMKI collaboration to explain anomalous signals around 17 MeV in excited $^{8}$ Be, $^{4}$ He and $^{12}$ C nuclear decays via internal pair creation. It has been subject to a global experimental and theoretical research program. The proposed direct search in $γ D \to e^{+} e^{-} p n$ can verify the existence of X17 through the production on a quasi-free neutron, and determine its quantum numbers separate from ongoing and planned nuclear-decay experiments. This is especially timely in view of the theoretical tension between results from the $^{12}$ C and $^{8}$ Be measurements. Using the plane-wave impulse approximation, we quantify the expected signal and background for pseudoscalar, vector and axial-vector X17 scenarios. We optimize the kinematics for the quasi-free neutron region with the upcoming MAGIX experiment at MESA in mind and show that for all three scenarios the X17 signal is clearly visible above the QED background.
↳ hep-phnucl-exnucl-th2 citations

Affiliations

first authorsco-authorsvia INSPIRE

Collider constraints on massive gravitons coupling to photons

Collider physics with no PDFs

Holographic baryons, dense matter and neutron star mergers

Quantum simulation of in-medium QCD jets: momentum broadening, gluon production, and entropy growth

Long-Lived Particles and the Quiet Sun

Femtoscopy of D mesons and light mesons upon unitarized effective field theories

X17 discovery potential from γD→e+e−pn with neutron tagging

Affiliations

Femtoscopy of $D$ mesons and light mesons upon unitarized effective field theories

X17 discovery potential from $γ D \to e^{+} e^{-} p n$ with neutron tagging