scholarly journals NON-SUSY AND SUSY ONE-STEP UNIFICATION

1998 ◽  
Vol 13 (26) ◽  
pp. 2153-2162 ◽  
Author(s):  
ABDEL PÉREZ-LORENZANA ◽  
ARNULFO ZEPEDA ◽  
WILLIAM A. PONCE
Keyword(s):  
Decay Rates ◽  
Coupling Constants ◽  
Gauge Models ◽  
The Standard Model ◽  
Low Energies ◽  
One Step ◽  
Standard Model Coupling ◽  
Model Independent ◽  
Supersymmetric Gauge ◽  
Experimental Values

We explore the possibility of achieving one-step unification of the standard model coupling constants within non-supersymmetric and supersymmetric gauge models, which at low energies have only the standard particle content. The constraints are the experimental values of αem, αs and sin 2θW at 102 GeV, and the lower bounds for FCNC and proton decay rates. The analysis is done in a model-independent way.

Z–Z' MIXING IN EXTENDED GAUGE MODELS FROM LEP 1990 DATA

1991 ◽  
Vol 06 (28) ◽  
pp. 2557-2567 ◽  
Author(s):  
G. BHATTACHARYA ◽  
A. DATTA ◽  
S. N. GANGGUL ◽  
A. RAYCHAUDHURI
Keyword(s):  
Standard Model ◽  
Cross Sections ◽  
Mixing Angle ◽  
Gauge Models ◽  
The Standard Model ◽  
Model Independent ◽  
Free Parameters ◽  
Combined Data

We have studied Z–Z' mixing in the extended gauge models of left-right and extra U(1) types. This has been carried out by performing simultaneous fits to the combined data of cross sections and asymmetries from the four LEP experiments which have collected over 550,000 Z0 decays in 1990. Two methods have been adopted to determine the mixing angle ξ0 by carrying out: (a) Standard Model dependent fits, where we calculate ρf and sin 2θf from the Standard Model, and (b) Standard Model independent fit, where we keep [Formula: see text] and [Formula: see text] as free parameters. Fitted values of the mixing angle ξ0, and deviation of the ρ parameter due to Z–Z' mixing are discussed.

scholarly journals Experimental input from $e^+e^-$ machines to hadronic contribution to muon (g-2)

2019 ◽  
Author(s):  
M. N. Achasov ◽  
R. R. Akhmetshin ◽  
A. N. Amirkhanov ◽  
A. V. Anisenkov ◽  
V. M. Aulchenko ◽  
...  
Keyword(s):  
Standard Model ◽  
Bound States ◽  
Theoretical Calculations ◽  
Current Status ◽  
Hadronic Contribution ◽  
The Standard Model ◽  
Low Energies ◽  
Belle Ii ◽  
Experimental Values ◽  
Precise Study

Precise study of the hadrons production in \bm{e^+e^-}𝐞+𝐞− annihilation at low energies provides important information about interactions of light quarks and spectroscopy of their bound states. These studies are especially important for theoretical calculations of the muon \bm{(g-2)}(𝐠−2) via the Standard Model because of the present difference between theoretical and experimental values exceeds three standard deviations. In this report we will discuss current status and recent results obtained by the CMD-3 experiment and will give a brief look to status of the BaBar and Belle II experiments.

scholarly journals Standard-Model Coupling Constants from Compositeness

2003 ◽  
Vol 18 (27) ◽  
pp. 1877-1885 ◽  
Author(s):  
J. Besprosvany
Keyword(s):  
Standard Model ◽  
Particle Interaction ◽  
Coupling Constants ◽  
Unified Theory ◽  
Grand Unified Theory ◽  
Coupling Constant ◽  
The Standard Model ◽  
Standard Model Coupling ◽  
Breaking Scale ◽  
Vector Particles

A coupling-constant definition is given based on the compositeness property of some particle states with respect to the elementary states of other particles. It is applied in the context of the vector-spin-1/2-particle interaction vertices of a field theory, and the standard model. The definition reproduces Weinberg's angle in a grand-unified theory. One obtains coupling values close to the experimental ones for appropriate configurations of the standard-model vector particles, at the unification scale within grand-unified models, and at the electroweak breaking scale.

scholarly journals Search for π0 decays to invisible particles

2021 ◽  
Vol 2021 (2) ◽  
Author(s):  
E. Cortina Gil ◽  
◽  
A. Kleimenova ◽  
E. Minucci ◽  
S. Padolski ◽  
...  
Keyword(s):  
Higgs Boson ◽  
Standard Model ◽  
Confidence Level ◽  
Branching Ratio ◽  
Standard Model Higgs Boson ◽  
Scalar Mixing ◽  
Upper Limit ◽  
Upper Limits ◽  
The Standard Model ◽  
Model Independent

Abstract The NA62 experiment at the CERN SPS reports a study of a sample of 4 × 109 tagged π0 mesons from K+ → π+π0(γ), searching for the decay of the π0 to invisible particles. No signal is observed in excess of the expected background fluctuations. An upper limit of 4.4 × 10−9 is set on the branching ratio at 90% confidence level, improving on previous results by a factor of 60. This result can also be interpreted as a model- independent upper limit on the branching ratio for the decay K+ → π+X, where X is a particle escaping detection with mass in the range 0.110–0.155 GeV/c2 and rest lifetime greater than 100 ps. Model-dependent upper limits are obtained assuming X to be an axion-like particle with dominant fermion couplings or a dark scalar mixing with the Standard Model Higgs boson.

scholarly journals Disentangling QCD and new physics in D → πℓ+ℓ−

2021 ◽  
Vol 2021 (4) ◽  
Author(s):  
Aoife Bharucha ◽  
Diogo Boito ◽  
Cédric Méaux
Keyword(s):  
Standard Model ◽  
Branching Ratio ◽  
Branching Ratios ◽  
New Physics ◽  
Operator Product ◽  
Beyond The Standard Model ◽  
Spectral Functions ◽  
The Standard Model ◽  
Model Independent ◽  
Weak Annihilation

Abstract In this paper we consider the decay D+ → π+ℓ+ℓ−, addressing in particular the resonance contributions as well as the relatively large contributions from the weak annihilation diagrams. For the weak annihilation diagrams we include known results from QCD factorisation at low q2 and at high q2, adapting the existing calculation for B decays in the Operator Product Expansion. The hadronic resonance contributions are obtained through a dispersion relation, modelling the spectral functions as towers of Regge-like resonances in each channel, as suggested by Shifman, imposing the partonic behaviour in the deep Euclidean. The parameters of the model are extracted using e+e− → (hadrons) and τ → (hadrons) + ντ data as well as the branching ratios for the resonant decays D+ → π+R(R → ℓ+ℓ−), with R = ρ, ω, and ϕ. We perform a thorough error analysis, and present our results for the Standard Model differential branching ratio as a function of q2. Focusing then on the observables FH and AFB, we consider the sensitivity of this channel to effects of physics beyond the Standard Model, both in a model independent way and for the case of leptoquarks.

SEARCH FOR NEW PHYSICS IN eμX DATA AT THE TEVATRON USING SLEUTH: A QUASI-MODEL-INDEPENDENT SEARCH STRATEGY FOR NEW PHYSICS

2001 ◽  
Vol 16 (supp01b) ◽  
pp. 888-890
Author(s):  
◽  
BRUCE KNUTESON
Keyword(s):  
Standard Model ◽  
Search Strategy ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Final States ◽  
Final State ◽  
The Standard Model ◽  
Model Independent

We present a quasi-model-independent search for physics beyond the standard model. We define final states to be studied, and construct a rule that identifies a set of variables appropriate for any particular final state. A new algorithm ("Sleuth") searches for regions of excess in the space of those variables and quantifies the significance of any detected excess. After demonstrating the sensititvity of the method, we apply it to the semi-inclusive channel eμX collected in ≈108 pb -1 of [Formula: see text] collisions at [Formula: see text] at the DØ experiment at the Fermilab Tevatron. We find no evidence of new high pT physics in this sample.

scholarly journals The framed Standard Model (II) — A first test against experiment

2015 ◽  
Vol 30 (30) ◽  
pp. 1530060
Author(s):  
Hong-Mo Chan ◽  
Sheung Tsun Tsou
Keyword(s):  
Standard Model ◽  
Renormalization Group Equation ◽  
Fermion Mass ◽  
Group Equation ◽  
Unknown Parameters ◽  
Mass Matrices ◽  
The Standard Model ◽  
Experimental Values ◽  
The Masses ◽  
Independent Parameters

Apart from the qualitative features described in Paper I (Ref. 1), the renormalization group equation derived for the rotation of the fermion mass matrices are amenable to quantitative study. The equation depends on a coupling and a fudge factor and, on integration, on 3 integration constants. Its application to data analysis, however, requires the input from experiment of the heaviest generation masses [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text] all of which are known, except for [Formula: see text]. Together then with the theta-angle in the QCD action, there are in all 7 real unknown parameters. Determining these 7 parameters by fitting to the experimental values of the masses [Formula: see text], [Formula: see text], [Formula: see text], the CKM elements [Formula: see text], [Formula: see text], and the neutrino oscillation angle [Formula: see text], one can then calculate and compare with experiment the following 12 other quantities [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], [Formula: see text], and the results all agree reasonably well with data, often to within the stringent experimental error now achieved. Counting the predictions not yet measured by experiment, this means that 17 independent parameters of the standard model are now replaced by 7 in the FSM.

scholarly journals Non-standard interactions in SMEFT confronted with terrestrial neutrino experiments

2021 ◽  
Vol 2021 (3) ◽  
Author(s):  
Yong Du ◽  
Hao-Lin Li ◽  
Jian Tang ◽  
Sampsa Vihonen ◽  
Jiang-Hao Yu
Keyword(s):  
Neutrino Oscillation ◽  
New Physics ◽  
Effective Field ◽  
Scalar Leptoquark ◽  
Double Chooz ◽  
The Standard Model ◽  
Reactor Neutrino ◽  
Model Independent ◽  
Neutrino Experiments ◽  
Individual Dimension

Abstract The Standard Model Effective Field Theory (SMEFT) provides a systematic and model-independent framework to study neutrino non-standard interactions (NSIs). We study the constraining power of the on-going neutrino oscillation experiments T2K, NOνA, Daya Bay, Double Chooz and RENO in the SMEFT framework. A full consideration of matching is provided between different effective field theories and the renormalization group running at different scales, filling the gap between the low-energy neutrino oscillation experiments and SMEFT at the UV scale. We first illustrate our method with a top- down approach in a simplified scalar leptoquark model, showing more stringent constraints from the neutrino oscillation experiments compared to collider studies. We then provide a bottom-up study on individual dimension-6 SMEFT operators and find NSIs in neutrino experiments already sensitive to new physics at ∼20 TeV when the Wilson coefficients are fixed at unity. We also investigate the correlation among multiple operators at the UV scale and find it could change the constraints on SMEFT operators by several orders of magnitude compared with when only one operator is considered. Furthermore, we find that accelerator and reactor neutrino experiments are sensitive to different SMEFT operators, which highlights the complementarity of the two experiment types.

scholarly journals Low-redshift measurement of the sound horizon through gravitational time-delays

2019 ◽  
Vol 632 ◽  
pp. A91 ◽  
Author(s):  
Nikki Arendse ◽  
Adriano Agnello ◽  
Radosław J. Wojtak
Keyword(s):  
Time Delay ◽  
Standard Model ◽  
Percent Level ◽  
Acoustic Oscillations ◽  
Microwave Background ◽  
Direct Measurements ◽  
The Standard Model ◽  
Model Independent ◽  
Competitive Test ◽  
Polynomial Expansions

Context. The matter sound horizon can be infered from the cosmic microwave background within the Standard Model. Independent direct measurements of the sound horizon are then a probe of possible deviations from the Standard Model. Aims. We aim at measuring the sound horizon rs from low-redshift indicators, which are completely independent of CMB inference. Methods. We used the measured product H(z)rs from baryon acoustic oscillations (BAO) together with supernovae Ia to constrain H(z)/H0 and time-delay lenses analysed by the H0LiCOW collaboration to anchor cosmological distances (∝ H0−1). Additionally, we investigated the influence of adding a sample of quasars with higher redshift with standardisable UV-Xray luminosity distances. We adopted polynomial expansions in H(z) or in comoving distances so that our inference was completely independent of any cosmological model on which the expansion history might be based. Our measurements are independent of Cepheids and systematics from peculiar motions to within percent-level accuracy. Results. The inferred sound horizon rs varies between (133 ± 8) Mpc and (138 ± 5) Mpc across different models. The discrepancy with CMB measurements is robust against model choice. Statistical uncertainties are comparable to systematics. Conclusions. The combination of time-delay lenses, supernovae, and BAO yields a distance ladder that is independent of cosmology (and of Cepheid calibration) and a measurement of rs that is independent of the CMB. These cosmographic measurements are then a competitive test of the Standard Model, regardless of the hypotheses on which the cosmology is based.

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