scholarly journals Relativistic effects in the search for new intra-atomic force with isotope shifts

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Minoru Tanaka ◽  
Yasuhiro Yamamoto
Keyword(s):  
Particle Physics ◽  
Relativistic Effects ◽  
Mass Range ◽  
New Physics ◽  
Wave Functions ◽  
Isotope Shifts ◽  
Atomic Force ◽  
The Standard Model ◽  
Nonrelativistic Calculation ◽  
New Physics Search

Abstract Isotope shift of atomic spectra is considered as a probe of new interaction between electrons and neutrons in atoms. We employ the method of seeking a breakdown of King’s linearity in the isotope shifts of two atomic transitions. In the present work, we evaluate the magnitudes of the nonlinearity using relativistic wave functions and the result is compared with that of nonrelativistic wave functions from our previous work. It turns out that the nonrelativistic calculation underestimates the nonlinearity owing to the new interaction in the mass range of the mediator greater than 1 MeV. Further, we find that the nonlinearity within the standard model of particle physics is significantly magnified by the relativistic effect in the $\text{p}_{1/2}$ state. To get rid of this obstacle in the new physics search, we suggest avoiding $\text{p}_{1/2}$ and that e.g. $\text{p}_{3/2}$ should be used instead.

scholarly journals The Search for Feebly Interacting Particles

2021 ◽  
Vol 71 (1) ◽  
pp. 279-313
Author(s):  
Gaia Lanfranchi ◽  
Maxim Pospelov ◽  
Philip Schuster
Keyword(s):  
Dark Matter ◽  
Particle Physics ◽  
Interaction Strength ◽  
New Physics ◽  
Fine Tuning ◽  
Experimental Program ◽  
Interacting Particles ◽  
Fundamental Physics ◽  
The Standard Model ◽  
The Universe

At the dawn of a new decade, particle physics faces the challenge of explaining the mystery of dark matter, the origin of matter over antimatter in the Universe, the apparent fine-tuning of the electroweak scale, and many other aspects of fundamental physics. Perhaps the most striking frontier to emerge in the search for answers involves New Physics at mass scales comparable to that of familiar matter—below the GeV scale but with very feeble interaction strength. New theoretical ideas to address dark matter and other fundamental questions predict such feebly interacting particles (FIPs) at these scales, and existing data may even provide hints of this possibility. Emboldened by the lessons of the LHC, a vibrant experimental program to discover such physics is underway, guided by a systematic theoretical approach that is firmly grounded in the underlying principles of the Standard Model. We give an overview of these efforts, their motivations, and the decadal goals that animate the community involved in the search for FIPs, and we focus in particular on accelerator-based experiments.

scholarly journals CP VIOLATIONS (AND MORE) AFTER THE FIRST TWO YEARS OF LHCB

2013 ◽  
Vol 53 (A) ◽  
pp. 528-533
Author(s):  
Giulio Auriemma
Keyword(s):  
Dark Matter ◽  
Dark Energy ◽  
Particle Physics ◽  
Hadron Collider ◽  
Higgs Sector ◽  
New Physics ◽  
Baryon Asymmetry ◽  
Open Problems ◽  
Cp Violations ◽  
The Standard Model

The most interesting cosmological open problems, baryon asymmetry, dark matter, inflation and dark energy, are not explained by the standard model of particle physics (SM). The final<br />goal of the Large Hadron Collider an experimental verification of the SM in the Higgs sector, and also a search for evidence of new physics beyond it. In this paper we will report some of the results obtained in 2010 and 2011, from the LHCb experiment dedicated to the study of CP violations and rare decays of heavy quarks.

scholarly journals Search for Charged Lepton Flavour Violation at CMS

2018 ◽  
Vol 182 ◽  
pp. 02090
Author(s):  
Swagata Mukherjee
Keyword(s):  
Gauge Symmetry ◽  
Standard Model ◽  
Particle Physics ◽  
Charged Lepton ◽  
New Physics ◽  
Lepton Sector ◽  
Lepton Flavour Violation ◽  
The Standard Model ◽  
Flavour Violation ◽  
Lepton Flavour

Lepton flavour is a conserved quantity in the standard model of particle physics, but it does not follow from an underlying gauge symmetry. After the discovery of neutrino oscillation, it has been established that lepton flavour is not conserved in the neutral sector. Thus the lepton sector is an excellent place to look for New Physics, and in this perspective the Charged Lepton Flavour Violation is interesting. Various extensions of the standard model predict lepton flavour violating decays that can be observed at LHC. This report summarises several searches for lepton flavour violation with data collected by the CMS detector.

scholarly journals Probing μτ flavor-violating solutions for the muon g − 2 anomaly at Belle II

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Syuhei Iguro ◽  
Yuji Omura ◽  
Michihisa Takeuchi
Keyword(s):  
Particle Physics ◽  
Standard Model Prediction ◽  
Mass Range ◽  
Loop Correction ◽  
Lepton Flavor ◽  
Highly Sensitive ◽  
The Standard Model ◽  
Belle Ii ◽  
The One ◽  
Mass Enhancement

Abstract The discrepancy between the measured value and the Standard Model prediction of the muon anomalous magnetic moment is one of the most important issues in the particle physics. It is known that introducing a mediator boson X with the μτ lepton flavor violating (LFV) couplings is one good solution to explain the discrepancy, due to the τ mass enhancement in the one-loop correction. In this paper, we study the signal of this model, i.e. the same-sign leptons, in the Belle II experiment, assuming the flavor-diagonal couplings are suppressed. We show that the Belle II experiment is highly sensitive to the scenario in the mediator mass range of O(1–10) GeV, using the e+e−→ μ±τ∓X → μ±μ±τ∓τ∓ process induced by the X .

Past, present and future of the muon g-2

2015 ◽  
Vol 39 ◽  
pp. 1560107
Author(s):  
A. E. Dorokhov ◽  
A. E. Radzhabov ◽  
A. S. Zhevlakov
Keyword(s):  
Quantum Electrodynamics ◽  
Particle Physics ◽  
Relativistic Quantum ◽  
Magnetic Moments ◽  
Structure Constant ◽  
New Physics ◽  
Fine Structure Constant ◽  
Measured Quantity ◽  
The Standard Model

The electron and muon anomalous magnetic moments (AMM) are measured in experiments and studied in the Standard Model (SM) with the highest precision accessible in particle physics. The comparison of the measured quantity with the SM prediction for the electron AMM provides the best determination of the fine structure constant. The muon AMM is more sensitive to the appearance of New Physics effects and, at present, there appears to be a three- to four-standard deviation between the SM and experiment. The lepton AMMs are pure relativistic quantum correction effects and therefore test the foundations of relativistic quantum field theory in general, and of quantum electrodynamics (QED) and SM in particular, with highest sensitivity. Special attention is paid to the studies of the hadronic contributions to the muon AMM which constitute the main source of theoretical uncertainties of the SM.

scholarly journals Searches for new physics with free neutrons and radioactive atomic nuclei

2021 ◽  
Vol 52 (4) ◽  
pp. 22-25
Author(s):  
N. Severijns
Keyword(s):  
Standard Model ◽  
Particle Physics ◽  
New Physics ◽  
Low Energy ◽  
Atomic Nuclei ◽  
The Standard Model ◽  
New Particles

The Standard Model of Particle Physics is very successful but does not explain several experimental observations. Extensions of it, invoking new particles or phenomena, could overcome this. Experiments in different energy domains allow testing these extensions and searching for new particles. Here focus is on low-energy experiments with neutrons and radioactive nuclei.

scholarly journals NoMoS: An R × B drift momentum spectrometer for beta decay studies

2019 ◽  
Vol 219 ◽  
pp. 04003 ◽  
Author(s):  
Daniel Moser ◽  
Hartmut Abele ◽  
Joachim Bosina ◽  
Harald Fillunger ◽  
Torsten Soldner ◽  
...  
Keyword(s):  
Standard Model ◽  
Angular Correlation ◽  
Beta Decay ◽  
Particle Physics ◽  
Correlation Coefficients ◽  
New Physics ◽  
Interference Term ◽  
Free Neutron ◽  
The Standard Model ◽  
Momentum Spectra

The beta decay of the free neutron provides several probes to test the Standard Model of particle physics as well as to search for extensions thereof. Hence, multiple experiments investigating the decay have already been performed, are under way or are being prepared. These measure the mean lifetime, angular correlation coefficients or various spectra of the charged decay products (proton and electron). NoMoS, the neutron decay products mo___mentum spectrometer, presents a novel method of momentum spectroscopy: it utilizes the R ×B drift effect to disperse charged particles dependent on their momentum in an uniformly curved magnetic field. This spectrometer is designed to precisely measure momentum spectra and angular correlation coefficients in free neutron beta decay to test the Standard Model and to search for new physics beyond. With NoMoS, we aim to measure inter alia the electron-antineutrino correlation coefficient a and the Fierz interference term b with an ultimate precision of Δa/a < 0.3% and Δb < 10−3 respectively. In this paper, we present the measurement principles, discuss measurement uncertainties and systematics, and give a status update.

scholarly journals A Heavy Scalar at the LHC from Vector-Boson Fusion

2018 ◽  
Vol 2018 ◽  
pp. 1-6
Author(s):  
Qiurong Mou ◽  
Sibo Zheng
Keyword(s):  
Standard Model ◽  
Vector Boson ◽  
Mass Range ◽  
New Physics ◽  
Vector Boson Fusion ◽  
Mixing Angle ◽  
The Standard Model ◽  
Scalar Mass ◽  
Event Simulations ◽  
Integrated Luminosity

A hypothetical scalar mixed with the standard model Higgs appears in few contexts of new physics. This study addresses the question what mass range is in the reach of 14 TeV LHC given different magnitudes of mixing angle α, where event simulations are based on production from vector-boson fusion channel and decays into SM leptons through WW or ZZ. It indicates that heavy scalar mass up to 539 GeV and 937 GeV can be excluded by integrated luminosity of 300 fb-1 and 3000 fb-1, respectively, for sin2α larger than 0.04.

scholarly journals Toward Three-Loop Feynman Massive Diagram Calculations

Symmetry ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 975
Author(s):  
Ievgen Dubovyk ◽  
Johann Usovitsch ◽  
Krzysztof Grzanka
Keyword(s):  
Differential Equation ◽  
Z Boson ◽  
Particle Physics ◽  
Numerical Solutions ◽  
New Physics ◽  
Weak Mixing ◽  
Feynman Integrals ◽  
Mixing Angles ◽  
The Standard Model ◽  
Decay Widths

There are many methods of searching for traces of the so-called new physics in particle physics. One of them, and the main focus of this paper, is athe study of the Z-boson decay in e+e− collisions. An improvement in the precision of calculations of the Standard Model (SM) electroweak pseudo-observables, such as scattering asymmetries, effective weak mixing angles, and decay widths, related to the Z-boson will meet severe experimental requirements at the planned e+e− colliders and will increase the chance to detect non-standard effects in experimental analysis. To reach this goal, one has to calculate the next order of perturbative SM theory, namely three-loop Feynman integrals. We discuss the complexity of the problem, as well as the methods crucial for completing three-loop calculations. We show several numerical solutions for some three-loop Feynman integrals using sector decomposition, Mellin–Barnes (MB), and differential equation methods.

scholarly journals Exact SMEFT formulation and expansion to $$ \mathcal{O} $$(v4/Λ4)

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Chris Hays ◽  
Andreas Helset ◽  
Adam Martin ◽  
Michael Trott
Keyword(s):  
Standard Model ◽  
Particle Physics ◽  
Input Parameter ◽  
Vacuum Expectation ◽  
Vacuum Expectation Value ◽  
New Physics ◽  
Specific Model ◽  
Effective Field ◽  
The Standard Model ◽  
Mass Dimension

Abstract The Standard Model Effective Field Theory (SMEFT) theoretical framework is increasingly used to interpret particle physics measurements and constrain physics beyond the Standard Model. We investigate the truncation of the effective-operator expansion using the geometric formulation of the SMEFT, which allows exact solutions, up to mass-dimension eight. Using this construction, we compare the exact solution to the expansion at $$ \mathcal{O} $$ O (v2/Λ2), partial $$ \mathcal{O} $$ O (v4/Λ4) using a subset of terms with dimension-6 operators, and full $$ \mathcal{O} $$ O (v4/Λ4), where v is the vacuum expectation value and Λ is the scale of new physics. This comparison is performed for general values of the coefficients, and for the specific model of a heavy U(1) gauge field kinetically mixed with the Standard Model. We additionally determine the input-parameter scheme dependence at all orders in v/Λ, and show that this dependence increases at higher orders in v/Λ.

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