Exotic Long-lived Particles

• Main Author: Jørgensen, Morten Dam
• Format: Book
• Language: English
• Published: The Niels Bohr Institute, Faculty of Science, University of Copenhagen 2014
• Subjects: Pingu; South Pole; South pole
• Online Access: https://curis.ku.dk/portal/da/publications/exotic-longlived-particles(e734c5d3-2c9c-4dc6-b34a-74fa819f21cd).html; https://soeg.kb.dk/permalink/45KBDK_KGL/fbp0ps/alma99121942467305763

With the LHC we hope to unravel the deepest secrets of reality: What is everything made of, what holds it together, do we understand the nature of matter at all? The subject of the defines is a search for new long-lived particles that could point to an explanation of what the dark matter in the universe is. If discovered these long-lived particles would break with 40 years of canonical physics, as the Standard Model of Particle physics would fail to explain its existence, something that would require Supersymmetry, extra spatial dimensions or even more exotic theories. In addition to this search, another type of long-lived particles, magnetic monopoles will be introduced. If monopoles are produced at the LHC they can be found stuck to the beam-pipe circulating the colliding particles. Last, new techniques for the future low-energy neutrino experiment PINGU will be presented. PINGU will be an upgrade to the larger 1 cubic kilometre IceCube detector at the South Pole. A search for hadronising long-lived massive particles at the Large Hadron Collider is conducted with the ATLAS detector. No excess events are found. Based on statistical analysis, upper limits on the production cross section are observed to be between 0.01 pb and 0.006 pb for colour octet particles (gluinos) with masses ranging from 300 GeV/c2 to 1400 GeV/c2, and 0.01 pb to 0.004 pb for colour triplet particles (stops and sbottoms) with masses ranging from 200 GeV/c2 to 900 GeV/c2. In the context of Supersymmetry with decoupled sfermion and sboson sectors (Split-SUSY), this gives a lower limit on the gluino mass of 989 GeV/c2, and 683 GeV/c2 for the stop mass and 618 GeV/c2 for the sbottom mass. In addition, a new method is presented that improves the speed (b ) estimation for long-lived particles in the ATLAS tile calorimeter with a factor of 7 improvement in resolution at low-b and a factor of 2 at high-b . An additional advantage of the new method is that the b -response is flat within the range of acceptance (0.2 < b 0.9) with an average b -resolution of 2.2%. The resolution of the speed estimate using the ATLAS pixel tracker has been improved by a factor of 3 at low b to a factor of 2 at higher b . The new method also introduces a flat response compared with previous methods. Furthermore, a simulation of magnetically charged monopoles is conducted. Based on simulation, magnetic monopoles with Dirac charges gD > 10 will predominantly be trapped in the LHC beam-pipe if produced within ATLAS. Two regions are identified as optimal for the extraction of the beampipe in a magnetometer-based search. Finally, a contribution has been made to the proposed IceCube lowenergy extension called PINGU which will improve the neutrino sensitivity to En 1 GeV. Motivated by indirect searches for Dark Matter annihilation in the sun, a likelihood based reconstruction method is developed that allows neutrino interaction vertex, energy, and direction estimation at this energy. The method provides a fast estimate based on a newly developed parametric model and multi-dimensional nested sampling. In addition, two neutrino flavour detection algorithms are developed which allow separation of charge-current muon events from other neutrino events.