scholarly journals Mixed modulus and anomaly mediation in light of the muon g − 2 anomaly

2021 ◽  
Vol 2021 (10) ◽  
Author(s):  
Kwang Sik Jeong ◽  
Junichiro Kawamura ◽  
Chan Beom Park
Keyword(s):  
Model Prediction ◽  
Standard Model Prediction ◽  
Gauge Coupling ◽  
New Physics ◽  
Supersymmetric Particle ◽  
Parameter Region ◽  
Anomaly Mediation ◽  
The Standard Model ◽  
Mixed Modulus ◽  
Robust Prediction

Abstract The new measurement of the anomalous magnetic moment of muon at the Fermilab Muon g− 2 experiment has strengthened the significance of the discrepancy between the standard model prediction and the experimental observation from the BNL measurement. If new physics responsible for the muon g− 2 anomaly is supersymmetric, one should consider how to obtain light electroweakinos and sleptons in a systematic way. The gauge coupling unification allows a robust prediction of the gaugino masses, indicating that the electroweakinos can be much lighter than the gluino if anomaly-mediated supersymmetry breaking is sizable. As naturally leading to mixed modulus-anomaly mediation, the KKLT scenario is of particular interest and is found capable of explaining the muon g− 2 anomaly in the parameter region where the lightest ordinary supersymmetric particle is a bino-like neutralino or slepton.

scholarly journals Standard Model prediction of the Bc lifetime

2021 ◽  
Vol 2021 (7) ◽  
Author(s):  
Jason Aebischer ◽  
Benjamín Grinstein
Keyword(s):  
Standard Model ◽  
Model Prediction ◽  
Strange Quark ◽  
Standard Model Prediction ◽  
New Physics ◽  
Operator Product ◽  
Special Focus ◽  
Third Order ◽  
Clear Cut ◽  
The Standard Model

Abstract Applying an operator product expansion approach we update the Standard Model prediction of the Bc lifetime from over 20 years ago. The non-perturbative velocity expansion is carried out up to third order in the relative velocity of the heavy quarks. The scheme dependence is studied using three different mass schemes for the $$ \overline{b} $$ b ¯ and c quarks, resulting in three different values consistent with each other and with experiment. Special focus has been laid on renormalon cancellation in the computation. Uncertainties resulting from scale dependence, neglecting the strange quark mass, non-perturbative matrix elements and parametric uncertainties are discussed in detail. The resulting uncertainties are still rather large compared to the experimental ones, and therefore do not allow for clear-cut conclusions concerning New Physics effects in the Bc decay.

scholarly journals Probing new physics scenarios of muon g − 2 via J/ψ decay at BESIII

2020 ◽  
Vol 2020 (10) ◽  
Author(s):  
Gorazd Cvetič ◽  
C. S. Kim ◽  
Donghun Lee ◽  
Dibyakrupa Sahoo
Keyword(s):  
Model Prediction ◽  
Magnetic Moment ◽  
Experimental Measurement ◽  
Anomalous Magnetic Moment ◽  
Numerical Study ◽  
Standard Model Prediction ◽  
Vector Boson ◽  
New Physics ◽  
Muon Anomalous Magnetic Moment ◽  
The Standard Model

Abstract The disagreement between the standard model prediction and the experimental measurement of muon anomalous magnetic moment can be alleviated by invoking an additional particle which is either a vector boson (X1) or a scalar (X0). This new particle, with the mass mX ≲ 2mμ, can be searched for in the decay J/ψ → μ−μ+X, where X is missing. Our numerical study shows that the search is quite feasible at the BESIII experiment in the parameter space allowed by muon g − 2 measurements.

scholarly journals A STUDY OF THE LEP AND SLD MEASUREMENTS OF Ab

2000 ◽  
Vol 15 (11n12) ◽  
pp. 761-774 ◽  
Author(s):  
J. H. FIELD ◽  
D. SCIARRINO
Keyword(s):  
Systematic Study ◽  
Model Prediction ◽  
Standard Model Prediction ◽  
Systematic Errors ◽  
New Physics ◽  
Data Sets ◽  
Statistical Fluctuation ◽  
Sensitive Data ◽  
Present Generation ◽  
The Standard Model

A systematic study is made of the data dependence of the parameter A b , that, since 1995, has shown a deviation from the Standard Model prediction of between 2.4 and 3.1 standard deviations. Issues addressed include: The effect of particular measurements, values found by individual experiments, LEP/SLD comparison, and the treatment of systematic errors. The effect, currently at the 2.4σ level, is found to vary in the range from 1.7σ to 2.9σ by excluding marginal or particularly sensitive data. Since essentially the full LEP and SLD Z-decay data sets are now analyzed the meaning of the deviation, (new physics or marginal statistical fluctuation) is unlikely to be given by the present generation of colliders.

scholarly journals THE EFFECT OF Z′ BOSON ON SAME-SIGN DIMUON CHARGE ASYMMETRY IN $B_q^0-\overline{B_q^0}$ SYSTEM

2013 ◽  
Vol 28 (15) ◽  
pp. 1350060 ◽  
Author(s):  
S. SAHOO ◽  
M. KUMAR ◽  
D. BANERJEE
Keyword(s):  
Model Prediction ◽  
Z Boson ◽  
Recent Observation ◽  
Standard Model Prediction ◽  
Charge Asymmetry ◽  
New Physics ◽  
Neutral Meson ◽  
Flavor Changing ◽  
The Standard Model ◽  
Meson Mixing

The recent observation of the same-sign dimuon charge asymmetry in the B system by the D0 collaboration has 3.9σ deviation from the standard model prediction. However, the recent LHCb data on Bs neutral-meson mixing do not accommodate the D0 collaboration result. In this paper, considering the effect of Z′-mediated flavor-changing neutral currents in the [Formula: see text] mixing, the same-sign dimuon charge asymmetry is calculated. We find the same-sign dimuon charge asymmetry is enhanced from its SM prediction and provides signals for new physics beyond the SM.

scholarly journals TENSION BETWEEN SCALAR/PSEUDOSCALAR NEW PHYSICS CONTRIBUTION TO Bs → μ+μ- AND B → Kμ+μ-

2010 ◽  
Vol 25 (13) ◽  
pp. 1099-1106 ◽  
Author(s):  
ASHUTOSH KUMAR ALOK ◽  
AMOL DIGHE ◽  
S. UMA SANKAR
Keyword(s):  
Standard Model ◽  
Model Prediction ◽  
Standard Model Prediction ◽  
Branching Ratio ◽  
New Physics ◽  
Strong Constraint ◽  
Maximum Value ◽  
The Standard Model ◽  
Experimental Errors ◽  
Current Bound

New physics in the form of scalar/pseudoscalar operators cannot lower the semileptonic branching ratio Br (B → K μ+μ-) below its standard model value. In addition, we show that the upper bound on the leptonic branching ratio Br (Bs → μ+μ-) sets a strong constraint on the maximum value of Br (B → K μ+μ-) in models with multiple Higgs doublets: with the current bound, Br (B → K μ+μ-) cannot exceed the standard model prediction by more than 2.5%. The conclusions hold true even if the new physics couplings are complex. However, these constraints can be used to restrict new physics couplings only if the theoretical and experimental errors in Br (B → K μ+μ-) are reduced to a few per cent. The constraints become relaxed in a general class of models with scalar/pesudoscalar operators.

scholarly journals Hadronic light-by-light scattering in the anomalous magnetic moment of the muon

2019 ◽  
Author(s):  
Nils Asmussen ◽  
Antoine Gerardin ◽  
Andreas Nyffeler ◽  
Harvey B. Meyer
Keyword(s):  
Light Scattering ◽  
Standard Model ◽  
Model Prediction ◽  
Magnetic Moment ◽  
Anomalous Magnetic Moment ◽  
Recent Progress ◽  
Standard Model Prediction ◽  
New Physics ◽  
The Standard Model ◽  
Discovery Potential

Hadronic light-by-light scattering in the anomalous magnetic moment of the muon a_\muaμ is one of two hadronic effects limiting the precision of the Standard Model prediction for this precision observable, and hence the new-physics discovery potential of direct experimental determinations of a_\muaμ. In this contribution, I report on recent progress in the calculation of this effect achieved both via dispersive and lattice QCD methods.

scholarly journals Flavor physics: Precision as an avenue to discovery

2020 ◽  
Vol 35 (01) ◽  
pp. 1930018
Author(s):  
Diego Guadagnoli
Keyword(s):  
Cp Violation ◽  
Standard Model ◽  
Flavor Physics ◽  
Standard Model Prediction ◽  
New Physics ◽  
Effective Theory ◽  
Theory Approach ◽  
Long Distance ◽  
The Standard Model ◽  
The Impact

This paper describes the work pursued in the years 2008–2013 on improving the Standard Model prediction of selected flavor-physics observables. The latter includes: (1) [Formula: see text], that quantifies indirect CP violation in the [Formula: see text] system and (2) the very rare decay [Formula: see text], recently measured at the LHC. Concerning point (1), the paper describes our reappraisal of the long-distance contributions to [Formula: see text],[Formula: see text] that have permitted to unveil a potential tension between CP violation in the [Formula: see text]- and [Formula: see text]-system. Concerning point (2), the paper gives a detailed account of various systematic effects pointed out in Ref. 4 and affecting the Standard Model [Formula: see text] decay rate at the level of 10% — hence large enough to be potentially misinterpreted as nonstandard physics, if not properly included. The paper further describes the multifaceted importance of the [Formula: see text] decays as new physics probes, for instance how they compare with [Formula: see text]-peak observables at LEP, following the effective-theory approach of Ref. 5. Both cases (1) and (2) offer clear examples in which the pursuit of precision in Standard Model predictions offered potential avenues to discovery. Finally, this paper describes the impact of the above results on the literature, and what is the further progress to be expected on these and related observables.

scholarly journals Lattice calculation of the hadronic leading order contribution to the muon g − 2

2020 ◽  
Vol 234 ◽  
pp. 01016
Author(s):  
Hartmut Wittig ◽  
Antoine Gérardin ◽  
Marco Cè ◽  
Georg von Hippel ◽  
Ben Hörz ◽  
...  
Keyword(s):  
Standard Model Prediction ◽  
Detailed Comparison ◽  
New Physics ◽  
Current Status ◽  
Leading Order ◽  
Lattice Calculation ◽  
Muon Anomalous Magnetic Moment ◽  
The Standard Model ◽  
Vacuum Polarisation

The persistent discrepancy of about 3.5 standard deviations between the experimental measurement and the Standard Model prediction for the muon anomalous magnetic moment, aµ, is one of the most promising hints for the possible existence of new physics. Here we report on our lattice QCD calculation of the hadronic vacuum polarisation contribution $ a_\mu ^{{\rm{hvp}}} $, based on gauge ensembles with Nf = 2 + 1 flavours of O(a) improved Wilson quarks. We address the conceptual and numerical challenges that one encounters along the way to a sub-percent determination of the hadronic vacuum polarisation contribution. The current status of lattice calculations of $ a_\mu ^{{\rm{hvp}}} $ is presented by performing a detailed comparison with the results from other groups.

scholarly journals Challenges for an axion explanation of the muon g − 2 measurement

2021 ◽  
Vol 2021 (9) ◽  
Author(s):  
Manuel A. Buen-Abad ◽  
JiJi Fan ◽  
Matthew Reece ◽  
Chen Sun
Keyword(s):  
Decay Constant ◽  
Standard Model Prediction ◽  
New Physics ◽  
Effective Theory ◽  
General Sense ◽  
Weak Scale ◽  
Initial Application ◽  
The Standard Model ◽  
Axion Decay Constant ◽  
Axion Decay

Abstract The discrepancy between the muon g − 2 measurement and the Standard Model prediction points to new physics around or below the weak scale. It is tantalizing to consider the loop effects of a heavy axion (in the general sense, also known as an axion-like particle) coupling to leptons and photons as an explanation for this discrepancy. We provide an updated analysis of the necessary couplings, including two-loop contributions, and find that the new physics operators point to an axion decay constant on the order of 10s of GeV. This poses major problems for such an explanation, as the axion couplings to leptons and photons must be generated at low scales. We outline some possibilities for how such couplings can arise, and find that these scenarios predict new charged matter at or below the weak scale and new scalars can mix with the Higgs boson, raising numerous phenomenological challenges. These scenarios also all predict additional contributions to the muon g−2 itself, calling the initial application of the axion effective theory into question. We conclude that there is little reason to favor an axion explanation of the muon g – 2 measurement relative to other models postulating new weak-scale matter.

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