897 research outputs found
Search for decays of stopped exotic long-lived particles produced in proton-proton collisions at √s = 13 TeV
A search is presented for the decays of heavy exotic long-lived particles (LLPs) that are produced in proton-proton collisions at a center-of-mass energy of 13 TeV at the CERN LHC and come to rest in the CMS detector. Their decays would be visible during periods of time well separated from proton-proton collisions. Two decay scenarios of stopped LLPs are explored: a hadronic decay detected in the calorimeter and a decay into muons detected in the muon system. The calorimeter (muon) search covers a period of sensitivity totaling 721 (744) hours in 38.6 (39.0) fb^(−1) of data collected by the CMS detector in 2015 and 2016. The results are interpreted in several scenarios that predict LLPs. Production cross section limits are set as a function of the mean proper lifetime and the mass of the LLPs, for lifetimes between 100 ns and 10 days. These are the most stringent limits to date on the mass of hadronically decaying stopped LLPs, and this is the first search at the LHC for stopped LLPs that decay to muons
Search for decays of stopped exotic long-lived particles produced in proton-proton collisions at = 13 TeV
A search is presented for the decays of heavy exotic long-lived particles (LLPs) that are produced in proton-proton collisions at a center-of-mass energy of 13 TeV at the CERN LHC and come to rest in the CMS detector. Their decays would be visible during periods of time well separated from proton-proton collisions. Two decay scenarios of stopped LLPs are explored: a hadronic decay detected in the calorimeter and a decay into muons detected in the muon system. The calorimeter (muon) search covers a period of sensitivity totaling 721 (744) hours in 38.6 (39.0) of data collected by the CMS detector in 2015 and 2016. The results are interpreted in several scenarios that predict LLPs. Production cross section limits are set as a function of the mean proper lifetime and the mass of the LLPs, for lifetimes between 100 ns and 10 days. These are the most stringent limits to date on the mass of hadronically decaying stopped LLPs, and this is the first search at the LHC for stopped LLPs that decay to muons
Collider Searches for Long-Lived Particles Beyond the Standard Model
Experimental tests of the Standard Model of particle physics (SM) find
excellent agreement with its predictions. Since the original formation of the
SM, experiments have provided little guidance regarding the explanations of
phenomena outside the SM, such as the baryon asymmetry and dark matter. Nor
have we understood the aesthetic and theoretical problems of the SM, despite
years of searching for physics beyond the Standard Model (BSM) at particle
colliders. Some BSM particles can be produced at colliders yet evade being
discovered, if the reconstruction and analysis procedures not matched to
characteristics of the particle. An example is particles with large lifetimes.
As interest in searches for such long-lived particles (LLPs) grows rapidly, a
review of the topic is presented in this article. The broad range of
theoretical motivations for LLPs and the experimental strategies and methods
employed to search for them are described. Results from decades of LLP searches
are reviewed, as are opportunities for the next generation of searches at both
existing and future experiments.Comment: 79 pages, 36 figures, submitted to Progress in Particle and Nuclear
Physic
Prospects for discovering supersymmetric long-lived particles with MoEDAL
We present a study on the possibility of searching for long-lived
supersymmetric partners with the MoEDAL experiment at the LHC. MoEDAL is
sensitive to highly ionising objects such as magnetic monopoles or massive
(meta)stable electrically charged particles. We focus on prospects of directly
detecting long-lived sleptons in a phenomenologically realistic model which
involves an intermediate neutral long-lived particle in the decay chain. This
scenario is not yet excluded by the current data from ATLAS or CMS, and is
compatible with astrophysical constraints. Using Monte Carlo simulation, we
compare the sensitivities of MoEDAL versus ATLAS in scenarios where MoEDAL
could provide discovery reach complementary to ATLAS and CMS, thanks to looser
selection criteria combined with the virtual absence of background. It is also
interesting to point out that, in such scenarios, in which charged staus are
the main long-lived candidates, the relevant mass range for MoEDAL is
compatible with a potential role of Supersymmetry in providing an explanation
for the anomalous events observed by the ANITA detector.Comment: 12 pages, 6 figures; preliminary results presented in
arXiv:1903.11022; matches published version in EPJ
The experimental status of direct searches for exotic physics beyond the standard model at the Large Hadron Collider
The standard model of particle physics is an extremely successful theory of
fundamental interactions, but it has many known limitations. It is therefore
widely believed to be an effective field theory that describes interactions
near the TeV scale. A plethora of strategies exist to extend the standard
model, many of which contain predictions of new particles or dynamics that
could manifest in proton-proton collisions at the Large Hadron Collider (LHC).
As of now, none have been observed, and much of the available phase space for
natural solutions to outstanding problems is excluded. If new physics exists,
it is therefore either heavy (i.e. slightly above the reach of current
searches) or hidden (i.e. currently indistinguishable from standard model
backgrounds). We summarize the existing searches, and discuss future directions
at the LHC.Comment: 33 pages, 7 figure
Exotic Phenomena Searches at Hadron Colliders
This review presents a selection of the final results of searches for various
exotic physics phenomena in proton-proton collisions at sqrt(s)=7 and 8 TeV
delivered by the LHC and collected with the ATLAS and CMS detectors in 2011 (5
fb-1) and in the first part of 2012 (4 fb-1). Searches for large extra
dimensions, gravitons, microscopic black holes, long-lived particles, dark
matter, and leptoquarks are presented in this report. No sign of new physics
beyond the Standard Model has been observed so far. In the majority of the
cases these searches set the most stringent limits to date on the
aforementioned new physics phenomena.Comment: 10 pages, 4 figures, Proceedings of the PIC 2012, Strbske Pleso,
Slovaki
Getting Stuck: Using Monosignatures to Test Highly Ionizing Particles
In this paper we argue that monojet and monophoton searches can be a
sensitive test of very highly ionizing particles such as particles with charges
and more generally particles that do not reach the outer parts
of the detector. 8 TeV monojet data from the CMS experiment excludes such
objects with masses in the range and charges
. This nicely complements searches for highly ionizing objects at
ALICE, ATLAS, CMS and LHCb. Expected improvements in these channels will extend
the sensitivity range to . This search strategy can
directly be generalized to other particles that strongly interact with the
detector material, such as e.g. magnetic monopoles.Comment: 15 pages, 8 figures, version published in PL
Physics reach of MoEDAL at LHC: magnetic monopoles, supersymmetry and beyond
MoEDAL is a pioneering experiment designed to search for highly ionising
messengers of new physics such as magnetic monopoles or massive (pseudo-)stable
charged particles, that are predicted to exist in a plethora of models beyond
the Standard Model. Its ground-breaking physics program defines a number of
scenarios that yield potentially revolutionary insights into such foundational
questions as, are there extra dimensions or new symmetries, what is the
mechanism for the generation of mass, does magnetic charge exist, what is the
nature of dark matter, and, how did the big-bang develop at the earliest times.
MoEDAL's purpose is to meet such far-reaching challenges at the frontier of the
field. The physics reach of the existing MoEDAL detector is discussed, giving
emphasis on searches for magnetic monopoles, supersymmetric (semi)stable
partners, doubly charged Higgs bosons, and exotic structures such as black-hole
remnants in models with large extra spatial dimensions and D-matter in some
brane theories.Comment: 17 pages, 8 figures; combines two invited talks in 5th International
Conference on New Frontiers in Physics (ICNFP 2016), 6-14 Jul 2016,
Kolymbari, Greece; based on arXiv:1405.7662, arXiv:1411.7651,
arXiv:1511.0174
Long-lived charged particles and multi-lepton signatures from neutrino mass models
Lepton number violation (LNV) is usually searched for by the LHC
collaborations using the same-sign di-lepton plus jet signature. In this paper
we discuss multi-lepton signals of LNV that can arise with experimentally
interesting rates in certain loop models of neutrino mass generation.
Interestingly, in such models the observed smallness of the active neutrino
masses, together with the high-multiplicity of the final states, leads in large
parts of the viable parameter space of such models to the prediction of
long-lived charged particles, that leave highly ionizing tracks in the
detectors. We focus on one particular 1-loop neutrino mass model in this class
and discuss its LHC phenomenology in some detail.Comment: 14 pages, 9 figure
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