547 research outputs found
Heavy Neutral Leptons at Muon Colliders
The future high-energy muon colliders, featuring both high energy and low
background, could play a critical role in our searches for new physics. The
smallness of neutrino mass is a puzzle of particle physics. Broad classes of
solutions to the neutrino puzzles can be best tested by seeking the partners of
SM light neutrinos, dubbed as heavy neutral leptons (HNLs), at muon colliders.
We can parametrize HNLs in terms of the mass and the mixing angle with
-flavor . In this work, we focus on the regime GeV
and study the projected sensitivities on the plane with the
full-reconstructable HNL decay into a hadronic and a charged lepton. The
projected reach in leads to the best sensitivities in the TeV
realm.Comment: 33 pages, 10 figure
Heavy Neutral Leptons from Stopped Muons and Pions
Stopped muons, which are generic in pion-at-rest experiments, can shed light
on heavy neutral leptons (HNLs) in unexplored parameter spaces. If the HNL is
lighter than the muon, the HNL can be produced from decays of muons and
pions.The HNL will travel from the production location and decay into visible
Standard Model (SM) modes, leaving signals inside downstream detectors. We find
that in the case that the HNL dominantly mixes with muon neutrinos, the LSND
constraint on the mixing angle squared is stronger than all the previous
constraints by more than an order of magnitude. In this study, we recast the
LSND measurement of the scattering. Future experiments such as PIP2-BD
could further improve the sensitivity, provided they can distinguish the HNL
events from backgrounds induced by the SM neutrinos.Comment: 13 pages, 2 figure
Flavor-changing light bosons with accidental longevity
We consider a model with a complex scalar field that couples to or
within the "longevity" window: in which and are the two different charged leptons.
Within such a mass window, even a relatively large coupling (e.g. of the size
commensurate with the current accuracy/discrepancy in the muon
experiment) leads to long lifetimes and macroscopic propagation distance
between production and decay points. We propose to exploit several existing
neutrino experiments and one future experiment to probe the parameter space of
this model. For the sector, we exploit the muonium decay branching
ratio and the production and decay sequence at the LSND experiment, excluding
the parametric region suggested by anomaly. For the
sector, we analyze three main production mechanisms of scalars at beam dump
experiments: the Drell-Yan process, the heavy meson decay, and the muon
scattering. We explore the constraints from the past CHARM and NuTeV
experiments, and evaluate sensitivity for the proposed beam dump experiment,
SHiP. The latter can thoroughly probe the parameter space relevant for the
anomaly.Comment: 30 pages, 9 figures and comments welcom
Top Yukawa Coupling Determination at High Energy Muon Collider
The Top Yukawa coupling profoundly influences several core mysteries linked
to the electroweak scale and the Higgs boson. We study the feasibility of
measuring the Top Yukawa coupling at high-energy muon colliders by examining
the high-energy dynamics of the weak boson fusion to top quark pair processes.
A deviation of the Top Yukawa coupling from the Standard Model would lead
modified process, violating unitarity at high
energy. Our analysis reveals that utilizing a muon collider with a
center-of-mass energy of 10 TeV and an integrated luminosity of 10 ab
allows us to investigate the Top Yukawa coupling with a precision surpassing
1.5\%, more than one order of magnitude better than the precision from channel at muon colliders. This precision represents a notable enhancement
compared to the anticipated sensitivities of the High-Luminosity LHC (3.4\%)
and those at muon colliders derived from the process.Comment: 33 pages, 13 figure
Detection of early-universe gravitational-wave signatures and fundamental physics
Detection of a gravitational-wave signal of non-astrophysical origin would be a landmark discovery, potentially providing a significant clue to some of our most basic, big-picture scientific questions about the Universe. In this white paper, we survey the leading early-Universe mechanisms that may produce a detectable signal—including inflation, phase transitions, topological defects, as well as primordial black holes—and highlight the connections to fundamental physics. We review the complementarity with collider searches for new physics, and multimessenger probes of the large-scale structure of the Universe.Peer reviewe
Detection of early-universe gravitational-wave signatures and fundamental physics
Detection of a gravitational-wave signal of non-astrophysical origin would be a landmark discovery, potentially providing a significant clue to some of our most basic, big-picture scientific questions about the Universe. In this white paper, we survey the leading early-Universe mechanisms that may produce a detectable signal—including inflation, phase transitions, topological defects, as well as primordial black holes—and highlight the connections to fundamental physics. We review the complementarity with collider searches for new physics, and multimessenger probes of the large-scale structure of the Universe.Peer reviewe
Searching for VHE gamma-ray emission associated with IceCube neutrino alerts using FACT, H.E.S.S., MAGIC, and VERITAS
The realtime follow-up of neutrino events is a promising approach to search for astrophysical
neutrino sources. It has so far provided compelling evidence for a neutrino point source: the
flaring gamma-ray blazar TXS 0506+056 was observed in coincidence with the high-energy neutrino IceCube-170922A detected by IceCube. The detection of very-high-energy gamma rays (VHE, E > 100 GeV) from this source helped establish the coincidence and constrained the modeling of the blazar emission at the time of the IceCube event. The four major imaging atmospheric Cherenkov telescope arrays (IACTs) - FACT, H.E.S.S., MAGIC, and VERITAS - operate an active follow-up program of target-of-opportunity observations of neutrino alerts sent by IceCube. This program has two main components. One are the observations of known gamma-ray sources around which a cluster of candidate neutrino events has been identified by IceCube (Gamma-ray Follow-Up, GFU). The second one is the follow-up of single high-energy neutrino candidate events of potential astrophysical origin such as IceCube-170922A. GFU has been recently upgraded by IceCube in collaboration with the IACT groups. We present here recent results from the IACT follow-up programs of IceCube neutrino alerts and a description of the upgraded IceCube GFU system
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