The angular momentum of two massless fields revisited

Pleitez, V.

doi:10.48550/arxiv.1508.01394

Cited by 7 publications

(8 citation statements)

References 22 publications

(18 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…From the functional forms of Eqs. ( 9) 2 In a non-Abelian gauge theory, the Landau-Yang theorem only forbids decays of spin-1 color-singlets to two gluons [44][45][46], because decay of a color-singlet requires that the gluons are indistinguishable. Tree-level amplitudes of spin-1 color-octet heavy quark pairs decaying to two gluons are widely known to vanish at tree-level [41,[47][48][49][50][51][52], but are non-zero at loop level [45].…”

Section: A Simple Discrimination Observablementioning

confidence: 99%

A Challenge for Discrimination of Color-Singlet versus Color-Octet Quarkonium Production

Larkoski

2022

Preprint

View full text Add to dashboard Cite

The precise mechanism for production of quarkonium at hadron colliders is still an open question. Within non-relativistic quantum chromodynamics, quarkonium production cross sections can be factorized into short-distance, perturbative contributions and universal, non-perturbative, longdistance matrix elements, and then summed over quantum numbers of the heavy quark pair. In principle, at short-distances, the heavy quark pair can be either in a color-singlet or color-octet state, and it is desirable to establish the relative contributions to compare with data and to make predictions in different experimental environments. From the explicit form of the lowest-order perturbative matrix elements for color-singlet and color-octet production, we show that the structure of the optimal observable for discrimination on phase space, the likelihood ratio, has strong dependence on the angular momentum state of the heavy quark pair. This presents an obstruction for construction of a single, robust discrimination observable that can be applied to production of an arbitrary quarkonium state.

show abstract

Section: A Simple Discrimination Observablementioning

confidence: 99%

A Challenge for Discrimination of Color-Singlet versus Color-Octet Quarkonium Production

Larkoski

2022

Preprint

View full text Add to dashboard Cite

show abstract

“…The Landau-Yang theorem in the context of non-Abelian gauge theories was already considered in Refs. [36,37,38,39]. The decisive difference of QCD to QED is the color degree of freedom which leads to more allowed quantum numbers for color antisymmetric states.…”

Section: Landau-yang Theoremmentioning

confidence: 99%

“…In the former case, the state J P = 1 + is removed from the possible states by the on-shell condition. For the parity odd case, the states J P = (2k + 1) − , with k a nonnegative integer, are removed also by the on-shell condition and the fact that the spatial dimension is three [34,38]. Since the gluons in the glueball are not on-shell, the on-shell condition is violated and the J = 1 states are not removed.…”

Section: Landau-yang Theoremmentioning

confidence: 99%

Higher spin glueballs from functional methods

Huber,

Fischer,

Sanchis-Alepuz

2021

Preprint

View full text Add to dashboard Cite

We calculate the glueball spectrum for spin up to J =4 and positive charge parity in pure Yang-Mills theory. We construct the full bases for J =0,1,2,3,4 and discuss the relation to gauge invariant operators. Using a fully self-contained truncation of Dyson-Schwinger equations as input, we obtain ground states and first and second excited states. Where available, we find good quantitative agreement with lattice results.

show abstract

“…Since Z is a spin-1 particle, it cannot couple at any order to a γγ final state due to the Landau-Yang theorem [39,40]. However, recent works claim that a spin-1 particle can couple to a gg state since gluons are colored [41][42][43][44]. Since we expect that limits coming from resonance searches in di-jet (jj) production and t t+jets production (tjj or t tjj) do not have sufficient sensitive to probe the relevant parameter space for the models considered, we ignore this possibility.…”

Section: Pseudo-scalar Np: Amentioning

confidence: 99%

Four-top as probe of light top-philic New Physics

Álvarez

Juste

Seoane

2019

J. High Energ. Phys.

View full text Add to dashboard Cite

We study the four-top (tttt) final state at the LHC as a probe for New Physics (NP) effects due to new particles that couple predominantly to the top quark and whose masses are below the top-quark-pair production threshold. We consider simple NP models containing a new particle with either spin 0, spin 1, or spin 2, and find benchmark points compatible with current experimental results. We find that interference effects between NP and QED amplitudes can be large, pointing out the necessity of NLO contributions to be explicitly computed and taken into account when NP is present. We examine kinematic differences between these models and the Standard Model (SM) at the parton level and the reconstructed level. In the latter case, we focus on events selected requiring two same-sign leptons and multiple jets. We investigate how the different Lorentz structure of the light NP affects the kinematic hardness, the polarization, the spin correlations, and the angular distributions of the parton-level and/or final-state particles. We find that spin-2 light NP would be identified by harder kinematics than the SM. We also show that the angular separation between the same-sign leptons is a sensitive observable for spin-0 NP. The spin-0 and spin-2 NP cases would also yield a signal in ttγγ with the invariant mass of the photons indicating the mass of the new particle. The spin-1 NP would be identified through an excess in four-top signal and slight or not modification in other observables, as for instance the lack of signal in ttγγ due to the Landau-Yang theorem. We comment on the opportunities that would open from the kinematic reconstruction of some of the top quarks in the tttt state. Our results provide new handles to probe for light top-philic NP as part of the ongoing experimental program of searches for four-top production at the LHC Run 2 and beyond. and predicted cross-sections is µ tttt = σ meas tttt /σ SM tttt = 1.05 +0.52 −0.48 . Therefore, an enhancement in the four-top production cross-section due to NP contributions of up to a factor of 1.5 (2.0) is still compatible with the measurements at about 1 s.d. (2 s.d.) level.This article is organized as follows. In Sect. 2 we describe a set of simple NP models containing new particles with either spin 0, spin 1, or spin 2, which couple predominantly to the top quark and whose masses are below the tt production threshold. We study existing constraints in these NP models arising from searches for di-photon (γγ) resonances and for four-top production, and we define suitable benchmark points in the model parameter space compatible with experimental results. In Sect. 3 we study the phenomenology of four-top production for some of these benchmark points. In Sect. 4 we present a discussion on the obtained results, and Sect. 5 contains the conclusions. We include three appendices to show more results on the full set of benchmark points, to describe the one-loop features of the NP models, and to summarize the numerical simulation details.

show abstract

The angular momentum of two massless fields revisited

Cited by 7 publications

References 22 publications

A Challenge for Discrimination of Color-Singlet versus Color-Octet Quarkonium Production

A Challenge for Discrimination of Color-Singlet versus Color-Octet Quarkonium Production

Higher spin glueballs from functional methods

Four-top as probe of light top-philic New Physics

Contact Info

Product

Resources

About