49 research outputs found
Proton decay at 1-loop
Proton decay is usually discussed in the context of grand unified theories.
However, as is well-known, in the standard model effective theory proton decay
appears in the form of higher dimensional non-renormalizable operators. Here,
we study systematically the 1-loop decomposition of the violating
operators. We exhaustively list the possible 1-loop ultra-violet completions of
these operators and discuss that, in general, two distinct classes of models
appear. Models in the first class need an additional symmetry in order to avoid
tree-level proton decay. These models necessarily contain a neutral particle,
which could act as a dark matter candidate. For models in the second class the
loop contribution dominates automatically over the tree-level proton decay,
without the need for additional symmetries. We also discuss possible
phenomenology of two example models, one from each class, and their possible
connections to neutrino masses, LHC searches and dark matter.Comment: 13 pages, 7 figure
Heavy neutral fermions at the high-luminosity LHC
Long-lived light particles (LLLPs) appear in many extensions of the standard
model. LLLPs are usually motivated by the observed small neutrino masses, by
dark matter or both. Typical examples for fermionic LLLPs (a.k.a. heavy neutral
fermions, HNFs) are sterile neutrinos or the lightest neutralino in R-parity
violating supersymmetry. The high luminosity LHC is expected to deliver up to
3/ab of data. Searches for LLLPs in dedicated experiments at the LHC could then
probe the parameter space of LLLP models with unprecedented sensitivity. Here,
we compare the prospects of several recent experimental proposals, FASER,
CODEX-b and MATHUSLA, to search for HNFs and discuss their relative merits.Comment: 21 pages, 6 figures; v2:references and minor comments added, plots
update
Revisiting the LHC reach in the displaced region of the minimal left-right symmetric model
We revisit discovery prospects for a long-lived sterile neutrino at the
Large Hadron Collider (LHC) in the context of left-right symmetric theories. We
focus on a displaced vertex search strategy sensitive to (GeV)
neutrino masses produced via a right-handed boson. Both on-shell and
off-shell Drell-Yan production of are considered. We estimate the reach
as a function of and . With TeV and 300/fb of
integrated luminosity, the LHC can probe neutrino masses as high as
GeV and around 6 TeV. The reach goes up to 11.5 TeV with 3000/fb
and GeV. This represents an improvement of a factor of 2 in
sensitivity with respect to earlier work.Comment: 6 pages, 1 figure. In v2: Numerical typo fixed, few clarifications on
the simulation and references added. Version accepted for publication in PR
LHC dijet constraints on double beta decay
We use LHC dijet data to derive constraints on neutrinoless double beta decay. Upper limits on cross sections for the production of ¿exotic¿ resonances, such as a right-handed W boson or a diquark, can be converted into lower limits on the double beta decay half-life for fixed choices of other parameters. Constraints derived from run-I data are already surprisingly strong and complementary to results from searches using same-sign dileptons plus jets. For the case of the left-right symmetric model, in case no new resonance is found in future runs of the LHC and assuming g(L) = g(R), we estimate a lower limit on the double beta decay half-life larger than 10(27) yr can be derived from future dijet data, except in the window of relatively light right-handed neutrino masses in the range 0.5 MeV to 50 GeV. Part of this mass window will be tested in the upcoming SHiP experiment. We also discuss current and future limits on possible scalar diquark contributions to double beta decay that can be derived from dijet data
Short-range mechanisms of neutrinoless double beta decay at the LHC
Lepton number violation (LNV) mediated by short- range operators can manifest itself in both neutrinoless double beta decay (0 nu beta beta) and in processes with same- sign dilepton final states at the LHC. We derive limits from existing LHC data at root s = 8 TeV and compare the discovery potential of the forthcoming root s = 14 TeV phase of the LHC with the sensitivity of current and future 0 nu beta beta decay experiments, assuming the short-range part of the 0 nu beta beta decay amplitude dominates. We focus on the first of two possible topologies triggered by one fermion and two bosons in the intermediate state. In all cases, except for the pure leptoquark mechanism, the LHC will be more sensitive than 0 nu beta beta decay in the future. In addition, we propose to search for a charge asymmetry in the final state leptons and to use different invariant mass peaks as a possible tool to discriminate the various possible mechanisms for LNV signals at the LHC
Probing Neutrino Dirac Mass in Left-Right Symmetric Models at the LHC and Next Generation Colliders
We assess the sensitivity of the LHC, its high energy upgrade, and a
prospective 100 TeV hadronic collider to the Dirac Yukawa coupling of the heavy
neutrinos in left-right symmetric models (LRSMs). We focus specifically on the
trilepton final state in regions of parameter space yielding prompt decays of
the right-handed gauge bosons () and neutrinos (). In the minimal
LRSM, the Dirac Yukawa couplings are completely fixed in terms of the mass
matrices for the heavy and light neutrinos. In this case, the trilepton signal
provides a direct probe of the Dirac mass term for a fixed and
mass. We find that while it is possible to discover the at the LHC,
probing the Dirac Yukawa couplings will require a 100 TeV collider. We
also show that the observation of the trilepton signal at the LHC would
indicate the presence of a non-minimal LRSM scenario.Comment: 28 pages, 10 figures, references adde
Neutrinoless double beta decay and lepton number violation at the LHC
10.1103/PhysRevD.88.011901This work was supported by EU Network Grant No. UNILHC PITN-GA-2009-237920 and by the Spanish MICINN Grants No. FPA2011-22975 and No. MULTIDARK CSD2009-00064, by the Generalitat Valenciana (Prometeo/2009/091), by Fondecyt Grants No. 11121557 and No. 1100582, and CONICYT Projects No. 791100017 and No. CONICYT/DFG-648. H. P. was supported by DGF Grant No. PA 803/6-1.Peer reviewe