Hadronic Channels Research Articles

AM3: An Open-source Tool for Time-dependent Lepto-hadronic Modeling of Astrophysical Sources

We present the Astrophysical Multimessenger Modeling (AM 3 ) software. AM 3 is a documented open-source software (source code at https://gitlab.desy.de/am3/am3; user guide and documentation at https://am3.readthedocs.io/en/latest/) that efficiently solves the coupled integro-differential equations describing the temporal evolution of the spectral densities of particles interacting in astrophysical environments, including photons, electrons, positrons, protons, neutrons, pions, muons, and neutrinos. The software has been extensively used to simulate the multiwavelength and neutrino emission from active galactic nuclei (including blazars), gamma-ray bursts, and tidal disruption events. The simulations include all relevant nonthermal processes, namely synchrotron emission, inverse Compton scattering, photon–photon annihilation, proton–proton and proton–photon pion production, and photo-pair production. The software self-consistently calculates the full cascade of primary and secondary particles, including nonlinear feedback processes and predictions in the time domain. It also allows the user to track separately the particle densities produced by means of each distinct interaction process, including the different hadronic channels. With its efficient hybrid solver combining analytical and numerical techniques, AM 3 combines efficiency and accuracy at a user-adjustable level. We describe the technical details of the numerical framework and present three examples of applications to different astrophysical environments.

Excited hadron channels in hadronization

The proper treatment of hadronic resonances plays an important role for many aspects of heavy ion collisions. We expect this to be the case also for hadronization, due to the large degeneracies of excited states, and the abundant production of hadrons from their decays. We show how a comprehensive treatment of excited meson states can be incorporated into quark recombination, and in extension, into Hybrid Hadronization. We discuss in detail the quantum mechanics of forming excited states, utilizing the Wigner distribution functions of angular momentum eigenstates of isotropic 3-D harmonic oscillators. We describe how resonance decays can be handled, based on a set of minimal assumptions, by creating an extension of hadron decays in PYTHIA 8. Finally, we present a study of hadron production by jets using PYTHIA and Hybrid Hadronization with excited mesons up to orbital angular momentum L = 4. We find that states up to L = 2 are produced profusely by quark recombination.

Resonance-aware NLOPS matching for off-shell toverline{t} + tW production with semileptonic decays

The increasingly high accuracy of top-quark studies at the LHC calls for a theoretical description of toverline{t} production and decay in terms of exact matrix elements for the full 2 → 6 process that includes the off-shell production and the chain decays of toverline{t} and tW intermediate states, together with their quantum interference. Corresponding NLO QCD calculations matched to parton showers are available for the case of dileptonic channels and are implemented in the bb4l Monte Carlo generator, which is based on the resonance-aware POWHEG method. In this paper, we present the first NLOPS predictions of this kind for the case of semileptonic channels. In this context, the interplay of off-shell toverline{t} + tW production with various other QCD and electroweak subprocesses that yield the same semileptonic final state is discussed in detail. On the technical side, we improve the resonance-aware POWHEG procedure by means of new resonance histories based on matrix elements, which enable a realistic separation of toverline{t} and tW contributions. Moreover, we introduce a general approach which makes it possible to avoid certain spurious terms that arise from the perturbative expansion of decay widths in any off-shell higher-order calculation, and which are large enough to jeopardise physical finite-width effects. These methods are implemented in a new version of the bb4l Monte Carlo generator, which is applicable to all dileptonic and semileptonic channels, and can be extended to fully hadronic channels. The presented results include a NLOPS comparison of off-shell against on-shell toverline{t} + tW production and decay, where we highlight various non-trivial aspects related to NLO and parton-shower radiation in leptonic and hadronic top decays.

LHC constraints on electroweakino dark matter revisited

We revisit LHC searches for heavy invisible particles by exploiting QCD initial state radiation. We recast a dijet signal region in a general multijet plus MET search by ATLAS. We find that non-trivial mass limit can be obtained for various models of the electroweakino sector with the present data in hadronic channels. The winos are bound to be heavier than $m_{\tilde W} \gtrsim {160}$ GeV and higgsinos $m_{\tilde h} \gtrsim {100}$ GeV, depending on the chargino-neutralino mass splitting. The expected exclusion limits at the LHC Run 3 with $\mathcal{L} = 300$ fb$^{-1}$ increase to $m_{\tilde W} \gtrsim {200}$ GeV and $m_{\tilde h} \gtrsim {130}$ GeV for winos and higgsino, respectively. This is the first LHC limit for promptly decaying nearly mass-degenerate winos.

Isospin-conserving hadronic decay of the D s1(2460) into D s π + π −

The internal structure of the charm-strange mesons and D s1(2460) are the subject of intensive studies. Their widths are small because they decay dominantly through isospin-breaking hadronic channels and . The D s1(2460) can also decay into the hadronic final states , conserving isospin. In that case there is, however, a strong suppression from phase space. We study the transition in the scenario that the D s1(2460) is a D * K hadronic molecule. The π π final state interaction is taken into account through dispersion relations. We find that the ratio of the partial widths of the obtained in the molecular picture is consistent with the existing experimental measurement. More interestingly, we demonstrate that the π + π − invariant mass distribution shows a double bump structure, which can be used to disentangle the hadronic molecular picture from the compact state picture for the D s1(2460)+. Predictions on the are also made.

Probing LHAASO galactic PeVatrons through gamma-ray and neutrino correspondence

ABSTRACT Recently, Large High Altitude Air Shower Observatory (LHAASO) has detected several Galactic point sources of ultra high energy (UHE; Eγ > 100 TeV) gamma-rays. These gamma-rays are possibly created in leptonic or hadronic interactions of cosmic rays (CRs) of PeV energies. In the hadronic channel (p − p interaction), the gamma-rays are accompanied by neutrinos. The detection of neutrinos is therefore crucial in understanding CR acceleration in such objects. To estimate the neutrino flux, we adopt the two LHAASO sources (J2226+6057, J1908+0621) found to be spatially associated with the supernova remnants (SNR G106.3+2.7, SNR G40.5–0.5). For these two sources, the detected TeV-PeV gamma-ray spectra are found to be unusually hard (with spectral index ∼1.8). We develop a model of gamma-ray and neutrino emission based on the above two prototypes. The neutrino fluxes from these two sources are found to be below the IceCube sensitivity, but are detectable in upcoming IceCube-Gen2 and KM3NeT experiments. We further estimate the neutrino fluxes from similar other 10 LHAASO PeVatron sources and most of them are found to be detectable in IceCube-Gen2 and KM3NeT. Finally, we explore our model parameters, in particular the spectral power-law index and estimate the future potential of the neutrino detectors to probe CR acceleration in such Galactic sources.

EFT analysis of leptophilic dark matter at future electron-positron colliders in the mono-photon and mono- Z channels

We consider the possibility that dark matter (DM) only interacts with the Standard Model leptons, but not quarks at tree level, and analyze the future lepton collider prospects of such leptophilic DM in the mono-photon and mono-$Z$ (both leptonic and hadronic) channels. Adopting a model-independent effective field theory framework, we consider all possible dimension-six operators of scalar-pseudoscalar (SP), vector-axial vector (VA), and tensor-axial tensor (TAT) types for a fermionic DM and derive the collider sensitivities on the effective cutoff scale $\mathrm{\ensuremath{\Lambda}}$ as a function of the DM mass. As a concrete example, we take the beam configurations of the International Linear Collider with $\sqrt{s}=1\text{ }\text{ }\mathrm{TeV}$ and $8\text{ }\text{ }{\mathrm{ab}}^{\ensuremath{-}1}$ integrated luminosity, including the effect of beam polarization, and show that it can probe leptophilic DM at $3\ensuremath{\sigma}$ level up to $\mathrm{\ensuremath{\Lambda}}$ values of 6.6, 8.8, and 7.1 TeV for the SP-, VA-, and TAT-type operators, respectively. This is largely complementary to the direct and indirect searches for leptophilic DM and can potentially provide the best-ever sensitivity in the low-mass DM regime.

Search for Pair-Produced vectorlike lepton singlet at the ILC by the XGBoost method

We study the pair production of the vector-like lepton singlet in the Wντ channel at the International Linear Collider (ILC) given that s=500 GeV. We analyse the characters of the signal and backgrounds. Through the detailed detector simulation and the Extreme Gradient Boosting (XGBoost) method, we obtain the excluding and discovering capabilities. For comparative study, we divide the search into the leptonic channel and the hadronic channel. We find that the statistical significance in the hadronic channel is better than the leptonic channel. The model includes only one free parameter, the vector-like lepton mass mτ′. Given that the polarized incident beams Pe−=0.8, Pe+=−0.3, the excluding and discovering capabilities can be given as follows: (1) the ILC can exclude the region mτ′∈ [180 GeV, 240 GeV] with an integrated luminosity of [3.49×10−2, 0.167] fb−1 ([0.286, 1.58] fb−1) in the hadronic channel (leptonic channel); (2) the ILC can discover the region mτ′∈ [180 GeV, 240 GeV] with an integrated luminosity of [0.185×10−2, 1.21] fb−1 ([1.74, 9.83] fb−1) in the hadronic channel (leptonic channel). These integrated luminosities can be achieved, which are lower than the maximum design integrated luminosity.

Search for the singlet vector-like lepton in Wντ channel at the TeV e+e− colliders

In this paper, we perform a search for the vector-like leptons (VLLs) in [Formula: see text] channel at the future TeV [Formula: see text] colliders such as the International Linear Collider (ILC) with 1[Formula: see text]TeV and Compact Linear Collider (CLIC) with 1.5[Formula: see text]TeV. We divide the signal into two decay channels, that is the pure leptonic channel and the fully hadronic channel. Through a detailed detector simulation, we display the excluding and discovering capability of VLLs at the ILC and CLIC. Compared to the pure leptonic channel, we find that it is more promising to detect the VLLs in the fully hadronic channel.

Do near-threshold molecular states mix with neighboring Q¯Q states?

The last two decades are marked by a renaissance in hadronic spectroscopy caused by the arrival of vast experimental information on exotic states in the spectrum of charmonium and bottomonium. Most of such states have properties at odds with the predictions of the quark model and reside very close to strong hadronic thresholds. Prominent examples are provided by the glorious $X(3872)$ charmonium-like state and the doubly charmed tetraquark $T_{cc}^+$ with the masses within less than 1 MeV from the $D\bar{D}^*$ and $DD^*$ open-charm thresholds, respectively. The universality of this feature hints towards the existence of a general pattern for such exotic states. In this work we discuss a possible generic mechanism for the formation of near-threshold molecular states as a result of the strong coupling of compact quark states with a hadronic continuum channel. The compact states that survive the strong coupling limit decouple from the continuum channel and therefore also from the formed hadronic molecule - if realised this scenario would provide a justification to treat hadronic molecules isolated, ignoring the possible influence from surrounding, compact quark-model states. We confront the phenomenology of the $D_{s1}(2460)$ and $D_{s1}(2536)$ with this picture and find consistency, although other explanations remain possible for those states.

Kinetic mass shifts of ρ(770) and K⁎(892) in Au+Au reactions at Ebeam = 1.23 A GeV

We explore the properties of the last generation of ρ(770) and K⁎(892) resonances created in Au+Au reactions at Elab=1.23AGeV via the reconstruction in the hadronic channel using the UrQMD model. Such resonance studies allow to obtain detailed information on the emission source in such reactions in a complementary way to di-lepton or HBT studies. We observe a freeze-out hierarchy and predict mass shifts for the ρ(770) resonance (Δmρ≈−330 MeV) and the K⁎(892) resonance (ΔmK⁎≈−30 MeV). These mass shifts are related to the regeneration cycles of each resonance species and are of purely kinetic origin. Experimentally our predictions can be tested using the GSI-HADES experiment or the lowest RHIC-BES energy.

Measurement of the π− -Ar total hadronic cross section at the LArIAT experiment

We present the first measurement of the negative pion total hadronic cross section on argon, which we performed at the Liquid Argon In A Testbeam (LArIAT) experiment. All hadronic reaction channels, as well as hadronic elastic interactions with scattering angle greater than 5~degrees are included. The pions have a kinetic energies in the range 100-700~MeV and are produced by a beam of charged particles impinging on a solid target at the Fermilab Test Beam Facility. LArIAT employs a 0.24~ton active mass Liquid Argon Time Projection Chamber (LArTPC) to measure the pion hadronic interactions. For this measurement, LArIAT has developed the ``thin slice method", a new technique to measure cross sections with LArTPCs. While generally higher than the prediction, our measurement of the ($\pi^-$,Ar) total hadronic cross section is in agreement with the prediction of the Geant4 model when considering a model uncertainty of $\sim$5.1\%.

Search for the singlet vector-like lepton through the pair production in the Wν τ channel at the ILC

We study the pair production of the vector-like lepton singlet decaying into at the International Linear Collider (ILC) with the center-of-mass in a simplified model. Considering the polarized degrees of electron and photon beams , , we implement a detailed detector simulation of the signal and backgrounds. For comparison, we investigate the search at leptonic channel and hadronic channel of the W boson, respectively. We find that the ILC can exclude (discover) the region [180 GeV, 240 GeV] with an integrated luminosity of ([0.305, 1.102] ) in the hadronic channel, and can exclude (discover) the region [180 GeV, 240 GeV] with an integrated luminosity of [1.83, 19.4] ([11.7, 117.8] ) in the leptonic channel. If these two results are combined, we find that the ILC can exclude (discover) the region [180 GeV, 240 GeV] with lower integrated luminosity.

Two-body hadronic decay of K+ in the presence of a circularly polarized laser field

In this study, we have investigated the two-body hadronic decay of the charged kaon, , in the presence of a laser field with circular polarization. We have derived, by analytical techniques, the laser-assisted decay width and the branching ratio of the charged kaon decay via the two-body hadronic channel. We have also taken into consideration the impressive results obtained for the laser-assisted charged kaon decay via the leptonic mode in order to understand more clearly the effect of the laser field on the quantities related to the charged kaon decay such as the decay width, the branching ratio and lifetime. A precise comparison of the ratios of hadronic-to-muonic decay in the presence of the laser field is made to show that the hadronic mode becomes slightly more important by increasing the laser field intensity.

Boosted top quark tagging and polarization measurement using machine learning

Machine learning techniques are used for treating jets as images to explore the performance of boosted top quark tagging. Tagging performances are studied in both hadronic and leptonic channels of top quark decay, employing a convolutional neural network (CNN) based technique along with boosted decision trees (BDT). This computer vision approach is also applied to distinguish between left and right polarized top quarks. In this context, an experimentally measurable asymmetry variable is proposed to estimate the polarization. Results indicate that the CNN based classifier is more sensitive to top quark polarization than the standard kinematic variables. It is observed that the overall tagging performance in the leptonic channel is better than the hadronic case, and the former also serves as a better probe for studying polarization.

Properties of ρ(770)0, K*(892), ϕ(1020), ∑(1385)±, Λ(1520) and Ξ(1530)0 resonances in heavy-ion collisions at a center of mass energy of and their reconstruction using the MPD detector at NICA

The short-lived hadronic resonances are used to study properties of the hot and dense medium produced in relativistic heavy-ion collisions. Due to their short lifetimes, the resonance yields and masses measured in the hadronic channels are sensitive to rescattering and regeneration effects in the hadronic phase. The measurement of resonances is foreseen in the physical program of the MPD experiment at NICA in heavy-ion collisions at , in the range of energies where extensive measurements of resonances are not experimentally available. In this contribution, we explore the sensitivity of the ρ(770)0, K*(892), ϕ(1020), ∑(1385)±, Λ(1520) and Ξ(1530)0 resonances measured in the hadronic decay channels to different stages of the heavy-ion collisions at NICA energies and report the feasibility studies for the reconstruction of resonances in the MPD setup

Constraints on gluon distribution functions in the nucleon and nucleus from open charm hadron production at the Electron-Ion Collider

The Electron-Ion Collider (EIC) at Brookhaven National Laboratory will be a precision Quantum Chromodynamics machine that will enable a vast physics program with electron+proton/ion collisions across a broad center-of-mass range. Measurements of hard probes such as heavy flavor in deep inelastic scatterings will be an essential component to the EIC physics program and are one of the detector R\&D driving aspects. In this paper we study the projected statistical precision of open charm hadron production through exclusive hadronic channel reconstruction with a silicon detector concept currently being developed using a PYTHIA-based simulation. We further study the impact of possible intrinsic charm in the proton on projected data, and estimate the constraint on the nuclear gluon parton distribution function (PDF) from the charm structure functions $F_{2}^{c\overline{c}}$ in $e$+Au collisions using a Bayesian PDF re-weighting technique. Our studies show the EIC will be capable delivering an unprecedented measurement of charm hadron production across a broad kinematic region and will provide strong constraints to both intrinsic charm and nuclear gluon PDFs.

A decaying neutralino as dark matter and its gamma ray spectrum

It is shown that a decaying neutralino in a supergravity unified framework is a viable candidate for dark matter. Such a situation arises in the presence of a hidden sector with ultraweak couplings to the visible sector where the neutralino can decay into the hidden sector’s lightest supersymmetric particle (LSP) with a lifetime larger than the lifetime of the universe. We present a concrete model where the MSSM/SUGRA is extended to include a hidden sector comprised of U(1)_{X_1} times U(1)_{X_2} gauge sector and the LSP of the hidden sector is a neutralino which is lighter than the LSP neutralino of the visible sector. We compute the loop suppressed radiative decay of the visible sector neutralino into the neutralino of the hidden sector and show that the decay can occur with a lifetime larger than the age of the universe. The decaying neutralino can be probed by indirect detection experiments, specifically by its signature decay into the hidden sector neutralino and an energetic gamma ray photon. Such a gamma ray can be searched for with improved sensitivity at Fermi-LAT and by future experiments such as the Square Kilometer Array (SKA) and the Cherenkov Telescope Array (CTA). We present several benchmarks which have a natural suppression of the hadronic channels from dark matter annihilation and decays and consistent with measurements of the antiproton background.

Multimessenger constraints on the dark matter interpretation of the Fermi -LAT Galactic Center excess

An excess of $\gamma$ rays in the data measured by the Fermi Large Area Telescope in the direction of the Galactic center has been reported in several publications. This excess, labeled as the Galactic center excess (GCE), is detected analyzing the data with different interstellar emission models, point source catalogs and analysis techniques. The characteristics of the GCE, recently measured with unprecedented precision, are all compatible with dark matter particles (DM) annihilating in the main halo of our Galaxy, even if other interpretations are still not excluded. We investigate the DM candidates that fit the observed GCE spectrum and spatial morphology. We assume a simple scenario with DM annihilating into a single channel but we inspect also more complicated models with two and three channels. We perform a search for a $\gamma$-ray flux from a list of 48 Milky Way dwarf spheroidal galaxies (dSphs) using state-of-the-art estimation of the DM density in these objects. Since we do not find any significant signal from the dSphs, we put upper limits on the annihilation cross section that result to be compatible with the DM candidate that fits the GCE. However, we find that the GCE DM signal is excluded by the AMS-02 $\bar{p}$ flux data for all hadronic and semi-hadronic annihilation channels unless the vertical size of the diffusion halo is smaller than 2 kpc -- which is in tension with radioactive cosmic ray fluxes and radio data. Furthermore, AMS-02 $e^+$ data rule out pure or mixed channels with a component of $e^+ e^-$. The only DM candidate that fits the GCE spectrum and is compatible with constraints obtained with the combined dSphs analysis and the AMS-02 $\bar{p}$ and $e^+$ data annihilates purely into $\mu^+\mu^-$, has a mass of 60 GeV and roughly a thermal cross section.

Search for the singlet vector-like lepton at future e^+ e^- colliders

Searching for the new particles beyond the standard model (SM) is an important way to probe new physics beyond the SM. In one class of new particles there are nonchiral color singlet fermions that couple to the SM leptons, that is vector-like leptons (VLLs), which have been widely concerned in experiment and theory. The existing literature shows that the singlet VLLs suffer from a big difficult challenge for discovery at future proton-proton colliders. In this paper, we study the prospects of searching for the singlet VLLs in pure leptonic and fully hadronic channels at e^+ e^- colliders. We find that there is an opportunity for excluding the region m_{tau ^{prime pm }} in [180 GeV, 240 GeV] with {mathcal {L}}in [3.0hbox { fb}^{-1}, 14.9hbox { fb}^{-1}] ([0.1hbox { fb}^{-1}, 0.3hbox { fb}^{-1}]) at ILC of sqrt{s} = 500 hbox { GeV}, the region m_{tau ^{prime pm }} in [240 GeV, 450 GeV] with {mathcal {L}} in [9.9hbox { fb}^{-1}, 23.1hbox { fb}^{-1}] ([0.2hbox { fb}^{-1}, 0.3hbox { fb}^{-1}]) at ILC of sqrt{s} = 1000 hbox { GeV} and the region m_{tau ^{prime pm }} in [450 GeV, 700 GeV] with {mathcal {L}} in [52.1hbox { fb}^{-1}, 197.9hbox { fb}^{-1}] ([2.21hbox { fb}^{-1}, 4.5hbox { fb}^{-1}]) at CLIC of sqrt{s} = 1500 hbox {GeV} in the pure leptonic (fully hadronic) channel. It is more optimistic for excluding and discovering the singlet VLL through the fully hadronic channel at future high energy e^+ e^- colliders.