scholarly journals Single Top as Window on Heavy Quarks and Other New Physics

2013 ◽  
Vol 2013 ◽  
pp. 1-8
Author(s):  
Andrea Giammanco
Keyword(s):  
Top Quarks ◽  
New Physics ◽  
Heavy Quarks ◽  
Single Top ◽  
First Time

This paper discusses what the study of the electroweak production of single top quarks can tell us about additional quark generations, and how to distinguish the new quarks hypothesis from other kinds of new physics. We also suggest some new studies that become possible for the first time thanks to the large statistics of single top quarks produced at the LHC.

scholarly journals Anomaly detection with convolutional Graph Neural Networks

2021 ◽  
Vol 2021 (8) ◽  
Author(s):  
Oliver Atkinson ◽  
Akanksha Bhardwaj ◽  
Christoph Englert ◽  
Vishal S. Ngairangbam ◽  
Michael Spannowsky
Keyword(s):  
Neural Networks ◽  
Anomaly Detection ◽  
Top Quarks ◽  
New Physics ◽  
Broad Applicability ◽  
Latent Space ◽  
Edge Features ◽  
Graph Neural Networks ◽  
Promising Avenue ◽  
Do So

Abstract We devise an autoencoder based strategy to facilitate anomaly detection for boosted jets, employing Graph Neural Networks (GNNs) to do so. To overcome known limitations of GNN autoencoders, we design a symmetric decoder capable of simultaneously reconstructing edge features and node features. Focusing on latent space based discriminators, we find that such setups provide a promising avenue to isolate new physics and competing SM signatures from sensitivity-limiting QCD jet contributions. We demonstrate the flexibility and broad applicability of this approach using examples of W bosons, top quarks, and exotic hadronically-decaying exotic scalar bosons.

scholarly journals Another SMEFT story: Z′ facing new results on ε′/ε, ∆MK and K → $$ \pi \nu \overline{\nu} $$

2020 ◽  
Vol 2020 (12) ◽  
Author(s):  
Jason Aebischer ◽  
Andrzej J. Buras ◽  
Jacky Kumar
Keyword(s):  
Renormalization Group ◽  
Mass Difference ◽  
Branching Ratios ◽  
New Physics ◽  
Matrix Elements ◽  
Isospin Breaking ◽  
Left Handed ◽  
The Standard Model ◽  
First Time ◽  
Group Effects

Abstract Recently the RBC-UKQCD lattice QCD collaboration presented new results for the hadronic matrix elements relevant for the ratio ε′/ε in the Standard Model (SM) albeit with significant uncertainties. With the present knowledge of the Wilson coefficients and isospin breaking effects there is still a sizable room left for new physics (NP) contributions to ε′/ε which could both enhance or suppress this ratio to agree with the data. The new SM value for the K0 − $$ {\overline{K}}^0 $$ K ¯ 0 mass difference ∆MK from RBC-UKQCD is on the other hand by 2σ above the data hinting for NP required to suppress ∆MK. Simultaneously the most recent results for K+ → $$ {\pi}^{+}\nu \overline{\nu} $$ π + ν ν ¯ from NA62 and for KL → $$ {\pi}^0\nu \overline{\nu} $$ π 0 ν ν ¯ from KOTO still allow for significant NP contributions. We point out that the suppression of ∆MK by NP requires the presence of new CP-violating phases with interesting implications for K → $$ \pi \nu \overline{\nu} $$ πν ν ¯ , KS → μ+μ− and KL → π0ℓ+ℓ− decays. Considering a Z′-scenario within the SMEFT we analyze the dependence of all these observables on the size of NP still allowed by the data on ε′/ε. The hinted ∆MK anomaly together with the εK constraint implies in the presence of only left-handed (LH) or right-handed (RH) flavour-violating Z′ couplings strict correlation between K+ → $$ {\pi}^{+}\nu \overline{\nu} $$ π + ν ν ¯ and KL → $$ {\pi}^0\nu \overline{\nu} $$ π 0 ν ν ¯ branching ratios so that they are either simultaneously enhanced or suppressed relative to SM predictions. An anticorrelation can only be obtained in the presence of both LH and RH couplings. Interestingly, the NP QCD penguin scenario for ε′/ε is excluded by SMEFT renormalization group effects in εK so that NP effects in ε′/ε are governed by electroweak penguins. We also investigate for the first time whether the presence of a heavy Z′ with flavour violating couplings could generate through top Yukawa renormalization group effects FCNCs mediated by the SM Z-boson. The outcome turns out to be very interesting.

scholarly journals Search for new physics via single-top production at the LHC

2007 ◽  
Vol 658 (1-3) ◽  
pp. 50-56 ◽  
Author(s):  
Qing-Hong Cao ◽  
Jose Wudka ◽  
C.-P. Yuan
Keyword(s):  
New Physics ◽  
Single Top

scholarly journals The history of the muon (g-2) experiments

2019 ◽  
Author(s):  
B. Lee Roberts
Keyword(s):  
Standard Model ◽  
Quantum Electrodynamics ◽  
National Laboratory ◽  
New Physics ◽  
Brookhaven National Laboratory ◽  
Muon Decay ◽  
Higgs Bosons ◽  
The Standard Model ◽  
History Of ◽  
First Time

I discuss the history of the muon (g-2)(g−2) measurements, beginning with the Columbia-Nevis measurement that observed parity violation in muon decay, and also measured the muon gg-factor for the first time, finding g_\mu=2gμ=2. The theoretical (Standard Model) value contains contributions from quantum electrodynamics, the strong interaction through hadronic vacuum polarization and hadronic light-by-light loops, as well as the electroweak contributions from the WW, ZZ and Higgs bosons. The subsequent experiments, first at Nevis and then with increasing precision at CERN, measured the muon anomaly a_\mu = (g_\mu-2)/2aμ=(gμ−2)/2 down to a precision of 7.3 parts per million (ppm). The Brookhaven National Laboratory experiment E821 increased the precision to 0.54 ppm, and observed for the first time the electroweak contributions. Interestingly, the value of a_\muaμ measured at Brookhaven appears to be larger than the Standard Model value by greater than three standard deviations. A new experiment, Fermilab E989, aims to improve on the precision by a factor of four, to clarify whether this result is a harbinger of new physics entering through loops, or from some experimental, statistical or systematic issue.

scholarly journals Search for Production of Single Top Quarks ViatcgandtugFlavor-Changing-Neutral-Current Couplings

2007 ◽  
Vol 99 (19) ◽  
Author(s):  
V. M. Abazov ◽  
B. Abbott ◽  
M. Abolins ◽  
B. S. Acharya ◽  
M. Adams ◽  
...  
Keyword(s):  
Neutral Current ◽  
Top Quarks ◽  
Single Top

scholarly journals Tagging single top quarks

2012 ◽  
Vol 86 (9) ◽  
Author(s):  
Felix Kling ◽  
Tilman Plehn ◽  
Michihisa Takeuchi
Keyword(s):  
Top Quarks ◽  
Single Top

scholarly journals TOP QUARK PHYSICS AT THE TEVATRON

2013 ◽  
Vol 28 (08) ◽  
pp. 1330013 ◽  
Author(s):  
FRÉDÉRIC DÉLIOT ◽  
YVONNE PETERS ◽  
VERONICA SORIN
Keyword(s):  
Top Quark ◽  
Top Quarks ◽  
New Physics ◽  
Beyond The Standard Model ◽  
Proton Antiproton ◽  
New Methods ◽  
Decay Properties ◽  
Large Program ◽  
The Standard Model ◽  
New Phenomena

The heaviest known elementary particle, the top quark, was discovered in 1995 by the CDF and D0 collaborations at the Tevatron proton–antiproton collider at Fermilab. Since its discovery, a large program was set in motion by the CDF and D0 collaborations to characterize the production and decay properties of top quarks, and investigate their potential for searches of new phenomena beyond the standard model. During the past 20 years, new methods were developed and implemented to improve the measurements and searches for new physics in the top quark sector. This paper reviews the achievements and results obtained through studies of the top quark at the Tevatron.

THE "TOP PRIORITY" AT THE LHC

2008 ◽  
Vol 23 (25) ◽  
pp. 4107-4124 ◽  
Author(s):  
TAO HAN
Keyword(s):  
Elementary Particle ◽  
Top Quark ◽  
Hadron Collider ◽  
Top Quarks ◽  
New Physics ◽  
Great Accuracy ◽  
Electroweak Symmetry Breaking ◽  
Electroweak Symmetry ◽  
High Luminosity ◽  
The Standard Model

The LHC (Large Hadron Collider) will be a top-quark factory. With 80 million pairs of top quarks and an additional 34 million single tops produced annually at the designed high luminosity, the properties of this particle will be studied to a great accuracy. The fact that the top quark is the heaviest elementary particle in the Standard Model with a mass right at the electroweak scale makes it tempting to contemplate its role in electroweak symmetry breaking, as well as its potential as a window to unknown new physics at the TeV scale. We summarize the expectations for top-quark physics at the LHC, and outline new physics scenarios in which the top quark is crucially involved.

Sign in / Sign up

Export Citation Format

Share Document