A
bstract
We calculate the cross-sections for the radiative formation of bound states by dark matter whose interactions are described in the non-relativistic regime by a Yukawa potential. These ...cross-sections are important for cosmological and phenomenological studies of dark matter with long-range interactions, residing in a hidden sector, as well as for TeV-scale WIMP dark matter. We provide the leading-order contributions to the cross-sections for the dominant capture processes occurring via emission of a vector or a scalar boson. We offer a detailed inspection of their features, including their velocity dependence within and outside the Coulomb regime, and their resonance structure. For pairs of annihilating particles, we compare bound-state formation with annihilation.
A
bstract
We study the prospects of a displaced-vertex search of sterile neutrinos at the Large Hadron Collider (LHC) in the framework of the neutrino-extended Standard Model Effective Field Theory (
...ν
SMEFT). The production and decay of sterile neutrinos can proceed via the standard active-sterile neutrino mixing in the weak current, as well as through higher-dimensional operators arising from decoupled new physics. If sterile neutrinos are long-lived, their decay can lead to displaced vertices which can be reconstructed. We investigate the search sensitivities for the ATLAS/CMS detector, the future far-detector experiments: AL3X, ANUBIS, CODEX-b, FASER, MATHUSLA, and MoEDAL-MAPP, and at the proposed fixed-target experiment SHiP. We study scenarios where sterile neutrinos are predominantly produced via rare charm and bottom mesons decays through minimal mixing and/or dimension-six operators in the
ν
SMEFT Lagrangian. We perform simulations to determine the potential reach of high-luminosity LHC experiments in probing the EFT operators, finding that these experiments are very competitive with other searches.
A
bstract
We present a method to determine the leading-order (LO) contact term contributing to the
nn → ppe
−
e
−
amplitude through the exchange of light Majorana neutrinos. Our approach is based on ...the representation of the amplitude as the momentum integral of a known kernel (proportional to the neutrino propagator) times the generalized forward Compton scattering amplitude
n
(
p
1
)
n
(
p
2
)
W
+
(
k
)
→
p
p
1
′
p
p
2
′
W
−
k
, in analogy to the Cottingham formula for the electromagnetic contribution to hadron masses. We construct model-independent representations of the integrand in the low- and high-momentum regions, through chiral EFT and the operator product expansion, respectively. We then construct a model for the full amplitude by interpolating between these two regions, using appropriate nucleon factors for the weak currents and information on nucleon-nucleon (
NN
) scattering in the
1
S
0
channel away from threshold. By matching the amplitude obtained in this way to the LO chiral EFT amplitude we obtain the relevant LO contact term and discuss various sources of uncertainty. We validate the approach by computing the analog
I
= 2
NN
contact term and by reproducing, within uncertainties, the charge-independence-breaking contribution to the
1
S
0
NN
scattering lengths. While our analysis is performed in the
MS
¯
scheme, we express our final result in terms of the scheme-independent renormalized amplitude
A
ν
p
p
′
at a set of kinematic points near threshold. We illustrate for two cutoff schemes how, using our synthetic data for
A
ν
, one can determine the contact-term contribution in any regularization scheme, in particular the ones employed in nuclear-structure calculations for isotopes of experimental interest.
We apply a fully automated extension of the R* operation capable of calculating higher-loop anomalous dimensions of n -point Green's functions of arbitrary, possibly nonrenormalizable, local quantum ...field theories. We focus on the case of the CP-violating Weinberg operator of the Standard Model effective field theory whose anomalous dimension is so far known only at one loop. We calculate the two-loop anomalous dimension in full QCD and the three-loop anomalous dimensions in the limit of pure Yang-Mills theory. We find sizable two-loop and large three-loop corrections, due to the appearance of a new quartic group invariant. We discuss phenomenological implications for electric dipole moments and future applications of the method.
Leptonic anomalous magnetic moments in ν SMEFT Cirigliano, Vincenzo; Dekens, Wouter; de Vries, Jordy ...
The journal of high energy physics,
08/2021, Letnik:
2021, Številka:
8
Journal Article
Recenzirano
Odprti dostop
A
bstract
We investigate contributions to the anomalous magnetic moments of charged leptons in the neutrino-extended Standard Model Effective Field Theory (
ν
SMEFT). We discuss how
ν
SMEFT operators ...can contribute to a lepton’s magnetic moment at one- and two-loop order. We show that only one operator can account for existing electronic and muonic discrepancies, assuming new physics appears above 1 TeV. In particular, we find that a right-handed charged current in combination with minimal sterile-active mixing can explain the discrepancy for sterile neutrino masses of
O
(100) GeV while avoiding direct and indirect constraints. We discuss how searches for sterile neutrino production at the (HL-)LHC, measurements of
h
→
μ
+
μ
−
and searches for
h
→
e
+
e
−
, neutrinoless double beta decay experiments, and improved unitarity tests of the CKM matrix can further probe the relevant parameter space.
A
bstract
We study the effective field theory obtained by extending the Standard Model field content with two singlets: a 750 GeV (pseudo-)scalar and a stable fermion. Accounting for collider ...productions initiated by both gluon and photon fusion, we investigate where the theory is consistent with both the LHC diphoton excess and bounds from Run 1. We analyze dark matter phenomenology in such regions, including relic density constraints as well as collider, direct, and indirect bounds. Scalar portal dark matter models are very close to limits from direct detection and mono-jet searches if gluon fusion dominates, and not constrained at all otherwise. Pseudo-scalar models are challenged by photon line limits and mono-jet searches in most of the parameter space.
The Gubaoquan area is located in the southern part of the Palaeozoic Beishan Orogenic Collage of the Central Asian Orogenic Belt in northwest China. Structural analysis of the Gubaoquan area has ...documented multiple phases of deformation, which challenge previous tectonic models and suggest that the eclogites formed through in-situ metamorphism. The study area is a highly deformed belt of metamorphic tectonites, intruded by syn-tectonic granitoids. The belt largely consists of D
3
fabrics that developed after peak metamorphism, with only local preservation of D
1
eclogite-facies fabrics in the cores of mafic boudins. Fabrics associated with D
1
–D
4
document a clockwise metamorphic trajectory, characterised by eclogite–facies metamorphism (D
1
) followed by a large decrease in pressure and small decrease in temperature (D
2
), high-temperature low-pressure conditions (D
3
) and greenschist-facies metamorphism (D
4
). D
2
–D
4
is associated with widespread N–S shortening and local extension. We propose that the metamorphic tectonite belt hosting the Gubaoquan eclogite represents Meso- to Neo-Proterozoic crust that underwent Ordovician–Silurian, north-directed subduction to various depths. The eclogite and its host were detached from the down-going slab, probably due to slab break-off and leading to extensive syn-tectonic magmatism. Exhumation probably occurred in an extruding-wedge-type setting. Convergence continued until the emplacement of the Silurian–Devonian granitoids.
A
bstract
Axions are introduced to explain the observed smallness of the
θ
¯
term of QCD. Standard Model extensions typically contain new sources of CP violation, for instance to account for the ...baryon asymmetry of the universe. In the presence of additional CP-violating sources a Peccei-Quinn mechanism does not remove all CP violation, leading to CP-odd interactions among axions and Standard Model fields. In this work, we use effective field theory to parametrize generic sources of beyond-the-Standard-Model CP violation. We systematically compute the resulting CP-odd couplings of axions to leptons and hadrons by using chiral perturbation theory. We discuss in detail the phenomenology of the CP-odd axion couplings and compare limits from axion searches, such as fifth force and monopole-dipole searches and astrophysics, to direct limits on the CP-violating operators from electric dipole moment experiments. While limits from electric dipole moment searches are tight, the proposed ARIADNE experiment can potentially improve the existing constraints in a window of axion masses.
A
bstract
We investigate electroweak baryogenesis within the framework of the Standard Model Effective Field Theory. The Standard Model Lagrangian is supplemented by dimension-six operators that ...facilitate a strong first-order electroweak phase transition and provide sufficient CP violation. Two explicit scenarios are studied that are related via the classical equations of motion and are therefore identical at leading order in the effective field theory expansion. We demonstrate that formally higher-order dimension-eight corrections lead to large modifications of the matter-antimatter asymmetry. The effective field theory expansion breaks down in the modified Higgs sector due to the requirement of a first-order phase transition. We investigate the source of the breakdown in detail and show how it is transferred to the CP-violating sector. We briefly discuss possible modifications of the effective field theory framework.
The role of leptons in electroweak baryogenesis de Vries, Jordy; Postma, Marieke; van de Vis, Jorinde
The journal of high energy physics,
04/2019, Letnik:
2019, Številka:
4
Journal Article
Recenzirano
Odprti dostop
A
bstract
We investigate the role of leptons in electroweak baryogenesis by studying a relatively simple framework inspired by effective field theory that satisfies all Sakharov conditions. In ...particular, we study the effectiveness of CP-violating source terms induced by dimension-six Yukawa interactions for quarks and charged leptons. Despite the relatively small Yukawa coupling, CP-violating source terms involving taus are quite effective and can account for the observed matter-antimatter asymmetry. We obtain analytical and numerical expressions for the total baryon asymmetry, the former providing important insight into what makes lepton CP violation relatively effective compared to quark CP violation. Leptons also play an important role if the CP-violating source involves top quarks. While the tau Yukawa coupling in the Standard Model is small, it significantly enhances the baryon asymmetry by transferring the chiral asymmetry in quarks, which is washed out by strong sphalerons, to a chiral asymmetry in leptons. We conclude that leptons should not be ignored even if CP violation is limited to the quark sector. The role of leptons can be further increased in scenarios of new physics with additional chiral-symmetry-breaking interactions between quarks and leptons, as can happen in models with additional Higgs bosons or leptoquarks. Finally, we study CP-violating dimension-six Yukawa interactions for lighter quarks and leptons but conclude that these lead to too small baryon asymmetries.
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