LIMITS FROM LEP 2 ON POSSIBLE ENHANCEMENT OF Re ∊′/∊ DUE TO ANOMALOUS GAUGE BOSON COUPLINGS

2001 ◽  
Vol 16 (supp01b) ◽  
pp. 669-671
Author(s):  
FRANCESCO TERRANOVA
Keyword(s):  
Standard Model ◽  
Low Energy ◽  
Hadron Colliders ◽  
Anomalous Couplings ◽  
The Past ◽  
The Poor ◽  
The Standard Model ◽  
Energy Processes ◽  
The Impact ◽  
Gauge Boson Couplings

It has been shown in the past that the real part of the ∊′/∊ ratio is particularly sensitive to anomalous gauge couplings that modify the Standard Model Lagrangian. Due to the loose bounds on these couplings coming from low energy processes and to the poor sensitivity of hadron colliders to couplings such as [Formula: see text], it has been argued that anomalous couplings could still produce an enhancement of Re ∊′/∊ bringing this observable closer to the experimental value obtained by KTeV, NA31 and NA48. The impact of the new measurements done at LEP2 in these years is discussed and new severe constraints to this hypothesis are determined.

scholarly journals IMPACT OF THE SUSY DECAYS ON THE SEARCH FOR THE MSSM HIGGS BOSONS AT THE LHC

1999 ◽  
Vol 14 (05) ◽  
pp. 359-368 ◽  
Author(s):  
A. DJOUADI
Keyword(s):  
Standard Model ◽  
Branching Ratios ◽  
Higgs Bosons ◽  
Hadron Colliders ◽  
Supersymmetric Extension ◽  
Decay Channels ◽  
Decay Modes ◽  
The Standard Model ◽  
The Impact ◽  
Minimal Supersymmetric Extension

In the context of the minimal supersymmetric extension of the Standard Model, we discuss the impact of the decays of the neutral Higgs bosons into supersymmetric particles, charginos/neutralinos and sfermions. We show that these decay modes could be dominant, when they are kinematically accessible, thus strongly suppressing the branching ratios for the decay channels which are used to detect the Higgs bosons at hadron colliders. These SUSY decay modes should therefore not be overlooked in the search for the Higgs particles at the LHC.

scholarly journals Bottom-flavored mono-tau tails at the LHC

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
David Marzocca ◽  
Ui Min ◽  
Minho Son
Keyword(s):  
Field Theory ◽  
Standard Model ◽  
Effective Field Theory ◽  
Effective Field ◽  
Low Energy ◽  
Final State ◽  
Lepton Flavor ◽  
The Standard Model ◽  
The Impact ◽  
Integrated Luminosity

Abstract We study the effective field theory sensitivity of an LHC analysis for the τν final state with an associated b-jet. To illustrate the improvement due to the b-tagging, we first recast the recent CMS analysis in the τν channel, using an integrated luminosity of 35.9 fb−1 at $$ \sqrt{s} $$ s = 13 TeV, and provide limits on all the dimension-six effective operators which contribute to the process. The expected limits from the b-tagged analysis are then derived and compared. We find an improvement of approximately ∼ 30% in the bounds for operators with a b quark. We also discuss in detail possible angular observables to be used as a discriminator between dimension-six operators with different Lorentz structure. Finally, we study the impact of these limits on some simplified scenarios aimed at addressing the observed deviations from the Standard Model in lepton flavor universality ratios of semileptonic B-meson decays. In particular, we compare the collider limits on those scenarios set by our analysis either with or without the b-tagging, assuming an integrated luminosity of 300 fb−1, with relevant low-energy flavor measurements.

scholarly journals Scalar leptoquark effects on $$B \rightarrow \mu \bar{\nu }$$ decay

2019 ◽  
Vol 79 (11) ◽  
Author(s):  
Wei-Shu Hou ◽  
Tanmoy Modak ◽  
Gwo-Guang Wong
Keyword(s):  
Standard Model ◽  
Parameter Space ◽  
Low Energy ◽  
Beyond The Standard Model ◽  
Meson Decays ◽  
Scalar Leptoquark ◽  
The Standard Model ◽  
The Impact ◽  
Energy Physics

AbstractPurely leptonic B meson decays provide unique probes for physics Beyond the Standard Model. We study the impact of a scalar leptoquark, $$S_1$$S1, on $$B \rightarrow \mu \bar{\nu }$$B→μν¯ decay. We find that, for $$m_{S_1}\sim 1\ \hbox {TeV}$$mS1∼1TeV, the $$S_1$$S1 leptoquark can modify the $$B \rightarrow \mu \bar{\nu }$$B→μν¯ rate significantly. Such a leptoquark can in principle also alter the $$B \rightarrow \tau \bar{\nu }$$B→τν¯ rate. However, current searches from LHC and low energy physics provide some constraints on the parameter space.

scholarly journals Flavour Anomalies in a U(1) SUSY Extension of the SM

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 191
Author(s):  
Alexander Bednyakov ◽  
Alfiia Mukhaeva
Keyword(s):  
Standard Model ◽  
Parameter Space ◽  
Gauge Boson ◽  
New Physics ◽  
Low Energy ◽  
Effective Theory ◽  
The Standard Model ◽  
Meson Mixing ◽  
Additional Anomaly ◽  
Lepton Flavour

Flavour anomalies have attracted a lot of attention over recent years as they provide unique hints for possible New Physics. Here, we consider a supersymmetric (SUSY) extension of the Standard Model (SM) with an additional anomaly-free gauge U(1) group. The key feature of our model is the particular choice of non-universal charges to the gauge boson Z′, which not only allows a relaxation of the flavour discrepancies but, contrary to previous studies, can reproduce the SM mixing matrices both in the quark and lepton sectors. We pay special attention to the latter and explicitly enumerate all parameters relevant for our calculation in the low-energy effective theory. We find regions in the parameter space that satisfy experimental constraints on meson mixing and LHC Z′ searches and can alleviate the flavour anomalies. In addition, we also discuss the predictions for lepton-flavour violating decays B+→K+μτ and B+→K+eτ.

scholarly journals The Impact of Excited Neutrinos onνν¯→γγProcess

2012 ◽  
Vol 2012 ◽  
pp. 1-8 ◽  
Author(s):  
S. C. İnan ◽  
M. Köksal
Keyword(s):  
Standard Model ◽  
Ultrahigh Energy ◽  
The Standard Model ◽  
The Impact

We examine the effect of excited neutrinos on the annihilation of relic neutrinos with ultrahigh energy cosmic neutrinos for theνν¯→γγprocess. The contributions of the excited neutrinos to the neutrino-photon decoupling temperature are calculated. We see that photon-neutrino decoupling temperature can be significantly reduced below the obtained value of the Standard Model with the impact of excited neutrinos.

A Note on Licenses in the Presence of Corruption

2017 ◽  
Vol 14 (3) ◽  
Author(s):  
Amy Farmer ◽  
Fabio Méndez ◽  
Andrew Samuel
Keyword(s):  
Standard Model ◽  
Regulatory Policies ◽  
The Standard Model ◽  
The Impact

Abstract We study the effectiveness of licenses in environments with corruption. We expand the standard model so that bribery is feasible not only when licenses are granted but also when enforced or verified. This modification alters many prior results on bribery and licensing significantly. Specifically, we show that in some cases penalties for bribery at the license-granting stage complement penalties for bribery at the permit-enforcement stage. In other cases, they act as substitutes for each other. These results are especially important for often used regulatory policies in which licenses are used in conjunction with some form of subsequent license verification. Thus, our model suggests that studying the impact of bribery at the license-granting stage should not be conducted without simultaneously studying bribery at the permit verification stage.

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 Testing lepton flavour universality with (semi)-leptonic $$\varvec{D_{(s)}}$$ decays

2020 ◽  
Vol 80 (2) ◽  
Author(s):  
Robert Fleischer ◽  
Ruben Jaarsma ◽  
Gabriël Koole
Keyword(s):  
Standard Model ◽  
Branching Ratios ◽  
Current Data ◽  
Leptonic Decays ◽  
Independent Analysis ◽  
The Standard Model ◽  
Model Independent ◽  
Pseudo Scalar ◽  
The Impact ◽  
Lepton Flavour

Abstract Data in B-meson decays indicate violations of lepton flavour universality, thereby raising the question about such phenomena in the charm sector. We perform a model-independent analysis of NP contributions in (semi)-leptonic decays of $$D_{(s)}$$D(s) mesons which originate from $$c \rightarrow d \bar{{\ell }} \nu _l$$c→dℓ¯νl and $$c \rightarrow s \bar{{\ell }} \nu _{\ell }$$c→sℓ¯νℓ charged-current interactions. Starting from the most general low-energy effective Hamiltonian containing four-fermion operators and the corresponding short-distance coefficients, we explore the impact of new (pseudo)-scalar, vector and tensor operators and constrain their effects through the interplay with current data. We pay special attention to the elements $$|V_{cd}|$$|Vcd| and $$|V_{cs}|$$|Vcs| of the Cabibbo–Kobayashi–Maskawa matrix and extract them from the $$D_{(s)}$$D(s) decays in the presence of possible NP decay contributions, comparing them with determinations utilizing unitarity. We find a picture in agreement with the Standard Model within the current uncertainties. Using the results from our analysis, we make also predictions for leptonic $$D_{(s)}^+ \rightarrow e^+ \nu _e$$D(s)+→e+νe modes which could be hugely enhanced with respect to their tiny Standard Model branching ratios. It will be interesting to apply our strategy at the future high-precision frontier.

scholarly journals Rb, Rc and New Physics: An Updated Model Independent Analysis

1997 ◽  
Vol 12 (04) ◽  
pp. 723-742 ◽  
Author(s):  
P. Bamert
Keyword(s):  
Standard Model ◽  
Neutral Current ◽  
New Physics ◽  
Low Energy ◽  
Coupling Constant ◽  
A Value ◽  
Independent Analysis ◽  
The Standard Model ◽  
Necessary And Sufficient ◽  
Do So

We analyze LEP and SLC data from the 1995 Summer Conferences as well as from low energy neutral current experiments for signals of new physics. The reasons for doing this are twofold: first to explain the deviations from the Standard Model observed in Rb and Rc and second to constrain nonstandard contributions to couplings of the Z0 boson to all fermions and to the oblique parameters. We do so by comparing the data with the Standard Model as well as with a number of test hypotheses concerning the nature of the new physics. These include nonstandard [Formula: see text]-, [Formula: see text]- and [Formula: see text]-couplings as well as the couplings of the Z0 to fermions of the entire first, second and third generations and universal corrections to all up- and down-type quark couplings (as can arise see for example in Z' mixing models). We find that nonstandard [Formula: see text] couplings are both necessary and sufficient to explain the data and in particular the Rb anomaly. It is not possible to explain Rb, Rc and a value of the strong coupling constant consistent with low energy determinations invoking only nonstandard [Formula: see text]- and [Formula: see text]-couplings. To do so one has to have also new physics contributions to the [Formula: see text] or universal corrections to all [Formula: see text] couplings.

TECHNIDILATON OR HIGGS?

1993 ◽  
Vol 08 (03) ◽  
pp. 275-283 ◽  
Author(s):  
EDI HALYO
Keyword(s):  
Standard Model ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Higgs Bosons ◽  
Low Energy ◽  
Gauge Bosons ◽  
Effective Lagrangian ◽  
The Standard Model

Interactions of the technidilaton with fermions and gauge bosons are obtained by constructing a low energy effective Lagrangian and using the fact that the technidilaton couples to the trace of the energy-momentum tensor Θµµ. Technidilaton’s interactions are compared with those of the Higgs bosons of the Standard Model with one or two scalar doublets.

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