Project F3: "Prompt lepton production in hadronic interactions"

The interpretation of data measured with neutrino telescopes depends in many ways on the understanding of the direct or, via neutrino production, indirect generation of muons in hadronic interactions. Thus, the rate of muon neutrino production determines the physics interpretation of atmospheric and astrophysical neutrino fluxes. As the production of muons also relates to the reconstruction of the mass composition and the cosmic-ray energy spectrum, a more detailed description of the hadronic interactions leading to muon production is needed both to allow for a better understanding of the cosmic-ray properties and an optimal background suppression for neutrino detection. This project pursues the goal of combining measurements of the complementary experiments IceCube and LHCb to investigate the role of promptly produced leptons. As products of high-energy primary atmospheric nucleus-nucleus interactions, the overwhelming number of muons and neutrinos are produced in decays of pions, kaons, and, to a smaller extent, in promptly decaying heavy mesons. Muons detected in IceCube have lost at least energies of \(\mathcal{O}\)(TeV), traversing the rock or ice overburden. Their parent hadrons are therefore mostly produced in the first cosmic-ray interactions. Thus, the so-called prompt muons from the primary interaction are dominantly produced by heavy hadrons decaying into leptons, Drell-Yan-processes, \(W^{\pm}\)-, \(Z^{0}\)-, or quarkonia decays. The detected muon bundles show a multiplicity and lateral distribution depending on the energy and mass of the primary nucleus, the interactions of the produced secondaries, and the relation of prompt muon production processes. For a complete understanding of the underlying physics, all muon production processes have to be disentangled. On a slightly shifted energy scale the neutrino production follows the muon production, so that, because of the small neutrino cross section, the prompt signature is expected to appear in the single neutrino-induced muon (or electron) flux.

In IceCube, in addition to the underground signal, the determination of the low-energy electromagnetic and hadronic part of the air shower with the surface detector component IceTop, and in the future also the shower shape recorded with the Cherenkov partial detector IceAct, will be available to narrow down the effects caused by heavy meson production.

In Phase 1 of CIM, we aim at the measurement of the prompt muon spectrum in pp collisions with data from the LHCb experiment and its upgrade. In addition, we will use the angular-dependent signatures of the recorded atmospheric muon and neutrino fluxes as well as, if applicable, the IceTop data from IceCube. Both approaches shall be connected via the use, evaluation, and tuning of Monte Carlo (MC) generators (e.g. EvtGen, EPOS, QGSJET, PYTHIA, SIBYLL, both within CORSIKA and the LHCb-MC-frame).

In Phase 2, we aim at a better understanding of the neutrino spectrum measured by IceCube by inferring a neutrino spectrum from muon spectra from (semi)leptonic hadron decays, measured by LHCb. Measurements of the forward prompt muon spectrum from proton-ion collisions will complement the LHCb program. The data will be used in the evaluation of MC generators.