scholarly journals Large hadron collider constraints on some simple $$Z^\prime $$ models for $$b\rightarrow s \mu ^+\mu ^-$$ anomalies

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
B. C. Allanach ◽  
J. M. Butterworth ◽  
Tyler Corbett

AbstractWe examine current Large Hadron Collider constraints on some simple $$Z^\prime $$ Z ′ models that significantly improve on Standard Model fits to $$b\rightarrow s \mu ^+\mu ^-$$ b → s μ + μ - transition data. The models that we consider are the ‘third family baryon number minus second family lepton number’ ($${B_3-L_2}$$ B 3 - L 2 ) model and the ‘third family hypercharge’ model and variants. The constraints are applied on parameter regions of each model that fit the $$b\rightarrow s \mu ^+\mu ^-$$ b → s μ + μ - transition data and come from high-mass Drell–Yan di-muons and measurements of Standard Model processes. This latter set of observables place particularly strong bounds upon the parameter space of the $${B_3-L_2}$$ B 3 - L 2 model when the mass of the $$Z^\prime $$ Z ′ boson is less than 300 GeV.

2018 ◽  
Vol 182 ◽  
pp. 02065
Author(s):  
Nicolas Köhler

Naturalness arguments for weak-scale supersymmetry favour supersymmetric partners of the third generation quarks with masses not too far from those of their Standard Model counterparts. Top or bottom squarks with masses less than or around one TeV can also give rise to direct pair production rates at the Large Hadron Collider (LHC) that can be observed in the data sample recorded by the ATLAS detector. This document presents recent ATLAS results from searches for direct top and bottom squark pair production considering both R-parity conserving and R-parity violating scenarios, using the data collected during the LHC Run 2 at a centre-of-mass energy of √s = 13 TeV.


2017 ◽  
Vol 32 (33) ◽  
pp. 1745005
Author(s):  
Fei Wang ◽  
Wenyu Wang ◽  
Lei Wu ◽  
Jin Min Yang ◽  
Mengchao Zhang

In this work, we investigate the degenerate heavy Higgs bosons in the Next-to-Minimal Supersymmetric Standard Model (NMSSM) by introducing vector-like particles. Such an extension is well motivated from the top-down view since some grand unified theories usually predict the existence of singlet scalars and vector-like particles at weak scale. Under the constraints from the Large Hadron Collider (LHC) and dark matter experiments, we find that (1) the null results of searching for high mass resonances have tightly constrained the parameter space; (2) two degenerate heavy singlet Higgs bosons [Formula: see text] and [Formula: see text] can sizably decay to [Formula: see text] invisibly. Therefore, search for the monojet events through the process [Formula: see text] may further test our scenario at the future LHC.


2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Linda M. Carpenter ◽  
Taylor Murphy ◽  
Matthew J. Smylie

Abstract In this work we study the collider phenomenology of color-octet scalars (sgluons) in minimal supersymmetric models endowed with a global continuous R symmetry. We systematically catalog the significant decay channels of scalar and pseudoscalar sgluons and identify novel features that are natural in these models. These include decays in nonstandard diboson channels, such as to a gluon and a photon; three-body decays with considerable branching fractions; and long-lived particles with displaced vertex signatures. We also discuss the single and pair production of these particles and show that they can evade existing constraints from the Large Hadron Collider, to varying extents, in large regions of reasonable parameter space. We find, for instance, that a 725 GeV scalar and a 350 GeV or lighter pseudoscalar can still be accommodated in realistic scenarios.


2006 ◽  
Vol 15 (01) ◽  
pp. 259-272
Author(s):  
TSAN UNG CHAN

Positive baryon numbers (A>0) and positive lepton numbers (L>0) characterize matter particles while negative baryon numbers and negative lepton numbers characterize antimatter particles. Matter particles and antimatter particles belong to two distinct classes of particles. Matter neutral particles are particles characterized by both zero baryon number and zero lepton number. This third class of particles includes mesons formed by a quark and an antiquark pair (a pair of matter particle and antimatter particle) and bosons which are messengers of known interactions (photons for electromagnetism, W and Z bosons for the weak interaction, gluons for the strong interaction). The antiparticle of a matter particle belongs to the class of antimatter particles, the antiparticle of an antimatter particle belongs to the class of matter particles. The antiparticle of a matter neutral particle belongs to the same class of matter neutral particles. A truly neutral particle is a particle identical with its antiparticle; it belongs necessarily to the class of matter neutral particles. All known interactions of the Standard Model conserve baryon number and lepton number; matter cannot be created or destroyed via a reaction governed by these interactions. Conservation of baryon and lepton number parallels conservation of atoms in chemistry; the number of atoms of a particular species in the reactants must equal the number of those atoms in the products. These laws of conservation valid for interaction involving matter particles are indeed valid for any particles (matter particles characterized by positive numbers, antimatter particles characterized by negative numbers, and matter neutral particles characterized by zero). Interactions within the framework of the Standard Model which conserve both matter and charge at the microscopic level cannot explain the observed asymmetry of our Universe. The strong interaction was introduced to explain the stability of nuclei: there must exist a powerful force to compensate the electromagnetic force which tends to cause protons to fly apart. The weak interaction with laws of conservation different from electromagnetism and the strong interaction was postulated to explain beta decay. Our observed material and neutral universe would signify the existence of another interaction that did conserve charge but did not conserve matter.


2008 ◽  
Vol 23 (32) ◽  
pp. 5117-5136 ◽  
Author(s):  
MONICA PEPE ALTARELLI ◽  
FREDERIC TEUBERT

LHCb is a dedicated detector for b physics at the LHC (Large Hadron Collider). In this paper we present a concise review of the detector design and performance together with the main physics goals and their relevance for a precise test of the Standard Model and search of New Physics beyond it.


2020 ◽  
Vol 2020 (8) ◽  
Author(s):  
Isabell Engeln ◽  
Pedro Ferreira ◽  
M. Margarete Mühlleitner ◽  
Rui Santos ◽  
Jonas Wittbrodt

Abstract We discuss the dark phases of the Next-to-2-Higgs Doublet model. The model is an extension of the Standard Model with an extra doublet and an extra singlet that has four distinct CP-conserving phases, three of which provide dark matter candidates. We discuss in detail the vacuum structure of the different phases and the issue of stability at tree-level of each phase. Taking into account the most relevant experimental and theoretical constraints, we found that there are combinations of measurements at the Large Hadron Collider that could single out a specific phase. The measurement of h125 → γγ together with the discovery of a new scalar with specific rates to τ+τ− or γγ could exclude some phases and point to a specific phase.


2013 ◽  
Vol 53 (A) ◽  
pp. 518-523
Author(s):  
Arno Straessner

The Large Hadron Collider (LHC) and the two multi-purpose detectors, ATLAS and CMS, have been operated successfully at record centre-of-mass energies of 7 ÷ 8TeV. This paper presents the main physics results from proton–proton collisions based on a total luminosity of 2 × 5 fb<sup>−1</sup>. The most recent results from Standard Model measurements, Standard Model and MSSM Higgs searches, as well as searches for supersymmetric and exotic particles are reported. Prospects for ongoing and future data taking are presented.


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