scholarly journals Effective Lagrangian approach to Higgs-mediated flavor changing neutral current top quark decays

2004 ◽  
Vol 70 (7) ◽  
Author(s):  
Adriana Cordero-Cid ◽  
M. A. Pérez ◽  
G. Tavares-Velasco ◽  
J. J. Toscano
Keyword(s):  
Top Quark ◽  
Neutral Current ◽  
Lagrangian Approach ◽  
Flavor Changing ◽  
Effective Lagrangian ◽  
Quark Decays ◽  
Flavor Changing Neutral Current

scholarly journals Studying flavor-changing neutral tqZ couplings: Current constraints and future prospects

2019 ◽  
Vol 34 (34) ◽  
pp. 1950278 ◽  
Author(s):  
Zenrō Hioki ◽  
Kazumasa Ohkuma ◽  
Akira Uejima
Keyword(s):  
Top Quark ◽  
Neutral Current ◽  
Branching Fractions ◽  
Hadron Collider ◽  
Coupling Constants ◽  
Flavor Changing ◽  
Lagrangian Framework ◽  
Effective Lagrangian ◽  
Flavor Changing Neutral Current ◽  
Invariant Dimension

Possible nonstandard tuZ and tcZ interactions, which induce flavor-changing neutral-current decays of the top quark, are studied in the effective-Lagrangian framework. The corresponding Lagrangian consists of four kinds of nonstandard couplings coming from [Formula: see text] invariant dimension-6 effective operators. The four coupling constants in each interaction are treated as complex numbers independent of each other and constraints on them are derived by using the present experimental limits of the branching fractions for [Formula: see text] and [Formula: see text] processes. Future improvements of those constraints are also discussed as well as possibilities of measurements of these couplings at the High-Luminosity Large Hadron Collider.

scholarly journals Probing the anomalous tqγ couplings through single top production at the future lepton–hadron colliders

2019 ◽  
Vol 34 (36) ◽  
pp. 1950298 ◽  
Author(s):  
E. Alici ◽  
M. Köksal
Keyword(s):  
Cross Sections ◽  
Top Quark ◽  
Neutral Current ◽  
New Physics ◽  
Main Reaction ◽  
Flavor Changing ◽  
Effective Lagrangian ◽  
Quark Flavor ◽  
The Future ◽  
Flavor Changing Neutral Current

The measurements of the top quark flavor changing neutral current interactions are one of the most important goals of the top quark physics program in the present and the future collider experiments. These measurements provide direct information on nonstandard interactions of the top quark. Within the framework of new physics beyond the Standard Model, these interactions can be defined by an effective Lagrangian. In this study, we have investigated the potential of the future [Formula: see text] colliders on the top quark flavor changing neutral current interactions through the subprocesses [Formula: see text], where [Formula: see text]. These subprocesses have been produced through the main reaction [Formula: see text] at the LHC-[Formula: see text], the FCC-[Formula: see text] and the SPPC-[Formula: see text]. For the main reaction, the total cross-sections have been calculated as a function of the anomalous [Formula: see text] couplings. In addition, sensitivities on [Formula: see text] at 95% Confidence Level have been calculated. We obtain that the best constraints on [Formula: see text] are at the order of [Formula: see text] which is four orders of magnitude better than the LHC’s experimental results.

scholarly journals SCALAR DARK MATTER EFFECTS IN HIGGS AND TOP QUARK DECAYS

2007 ◽  
Vol 22 (25n28) ◽  
pp. 2121-2129 ◽  
Author(s):  
XIAO-GANG HE ◽  
HO-CHIN TSAI ◽  
TONG LI ◽  
XUE-QIAN LI
Keyword(s):  
Dark Matter ◽  
Top Quark ◽  
Neutral Current ◽  
Higgs Doublet ◽  
Tree Level ◽  
Flavor Changing ◽  
Higgs Decay ◽  
Dark Matter Relic Density ◽  
Flavor Changing Neutral Current ◽  
Two Higgs Doublet Model

We study possible observational effects of scalar dark matter, the darkon D, in Higgs h and top quark t decay processes, h → DD and t → cDD in the minimal Standard Model (SM) and its two Higgs doublet model (THDM) extension supplemented with a SM singlet darkon scalar field D. We find that the darkon D can have a mass in the range of sub-GeV to several tens of GeV, interesting for LHC and ILC colliders, to produce the required dark matter relic density. In the SM with a darkon, t → cDD only occurs at loop level giving a very small rate, while the rate for Higgs decay h → DD can be large. In THDM III with a darkon, where tree level flavor changing neutral current (FCNC) interaction exists, a sizable rate for t → cDD is also possible.

scholarly journals IMPLICATIONS OF $D^0$--$\overline{D^0}$ ON THE RARE TOP QUARK DECAYS t → uγ AND t → ug

2009 ◽  
Vol 24 (39) ◽  
pp. 3219-3226 ◽  
Author(s):  
J. I. ARANDA ◽  
A. CORDERO-CID ◽  
F. RAMÍREZ-ZAVALETA ◽  
J. J. TOSCANO ◽  
E. S. TUTUTI
Keyword(s):  
Top Quark ◽  
Mass Difference ◽  
Branching Ratios ◽  
Lagrangian Approach ◽  
Effective Lagrangian ◽  
Quark Decays ◽  
Model Independent

The recently observed mass difference of the [Formula: see text] mixing is used to predict the branching ratios of the rare top quark decays t → uγ and t → ug in a model-independent way using the effective Lagrangian approach. It is found that Br (t → uγ) < 4 × 10-4 and Br (t → ug) < 2 × 10-3, which may still be within reach of the LHC collider.

scholarly journals NEXT-TO-NEXT-TO-LEADING ORDER SOFT AND VIRTUAL CORRECTIONS FOR QCD, HIGGS AND SUSY PROCESSES

2004 ◽  
Vol 19 (06) ◽  
pp. 405-419 ◽  
Author(s):  
NIKOLAOS KIDONAKIS
Keyword(s):  
Top Quark ◽  
W Boson ◽  
Neutral Current ◽  
Leading Order ◽  
Large Transverse Momentum ◽  
Hadron Colliders ◽  
Unified Approach ◽  
Anomalous Couplings ◽  
Flavor Changing ◽  
Flavor Changing Neutral Current

We review recent advances in the calculation of higher-order soft-gluon corrections for a variety of QCD, Higgs, and SUSY processes in hadron colliders. A unified approach and master formulas for next-to-next-to-leading order soft and virtual corrections are discussed. We present some applications of the formalism to top quark pair production at the Tevatron and the LHC, top production via anomalous couplings in flavor-changing neutral-current processes, W boson hadroproduction at large transverse momentum, and charged Higgs production at the LHC.

Search for Flavor-Changing Neutral Current Decays of the Top Quark inpp¯Collisions ats=1.8TeV

1998 ◽  
Vol 80 (12) ◽  
pp. 2525-2530 ◽  
Author(s):  
F. Abe ◽  
H. Akimoto ◽  
A. Akopian ◽  
M. G. Albrow ◽  
S. R. Amendolia ◽  
...  
Keyword(s):  
Top Quark ◽  
Neutral Current ◽  
Flavor Changing ◽  
Flavor Changing Neutral Current
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