Rare b decays meet high-mass Drell-Yan Greljo, Admir; Salko, Jakub; Smolkovič, Aleks ...
The journal of high energy physics,
05/2023, Volume:
2023, Issue:
5
Journal Article
Peer reviewed
Open access
A
bstract
Rare
b
hadron decays are considered excellent probes of new semileptonic four-fermion interactions of microscopic origin. However, the same interactions also correct the high-mass Drell-Yan ...tails. In this work, we revisit the first statement in the context of this complementarity and chart the space of short-distance new physics that could show up in rare
b
decays. We analyze the latest
b → qℓ
+
ℓ
−
measurements, where
q
=
d
or
s
and
ℓ
=
e
or
μ
, including the most recent LHCb
R
K
∗
update, together with the latest charged and neutral current high-mass Drell-Yan data,
pp → ℓν
and
pp → ℓ
+
ℓ
−
. We implement a sophisticated interpretation pipeline within the flavio framework, allowing us to investigate the multidimensional SMEFT parameter space thoroughly and efficiently. To showcase the new functionalities of flavio, we construct several explicit models featuring either a
Z
′ or a leptoquark, which can explain the tension in
b
→
sμ
+
μ
−
angular distributions and branching fractions while predicting lepton flavor universality (LFU) ratios to be SM-like,
R
K
∗
≈
R
K
∗
SM
, as indicated by the recent data. Those models are then confronted against the global likelihood, including the high-mass Drell-Yan, either finding tensions or compatibility.
A
bstract
In the case where the Standard Model is extended by one heavy Majorana fermion, the branching fractions of semileptonic meson decays into same-sign and opposite-sign dileptons are expected ...to be of the same order. As we discuss here, this need not be the case in extensions by at least two sterile fermions, due to the possible destructive and constructive interferences that might arise. Depending on the
CP
violating phases, one can have an enhancement of the lepton number violating modes and suppression of the lepton number conserving ones (and vice-versa). We explore for the first time the interference effects in semileptonic decays, and illustrate them for a future observation of kaon decays at NA62. We also argue that a non-observation of a given mode need not be interpreted in terms of reduced active-sterile mixings, but that it could instead be understood in terms of interference effects due to the presence of several sterile states; in particular, for different-flavour final state charged leptons, observing a lepton number conserving process and not a lepton number violating one does not rule out that the mediators are Majorana fermions.
Detection of a gravitational-wave signal of non-astrophysical origin would be a landmark discovery, potentially providing a significant clue to some of our most basic, big-picture scientific ...questions about the Universe. In this white paper, we survey the leading early-Universe mechanisms that may produce a detectable signal—including inflation, phase transitions, topological defects, as well as primordial black holes—and highlight the connections to fundamental physics. We review the complementarity with collider searches for new physics, and multimessenger probes of the large-scale structure of the Universe.
A
bstract
A search is performed for events consistent with the pair production of a new heavy particle that acts as a mediator between a dark sector and normal matter, and that decays to a light ...quark and a new fermion called a dark quark. The search is based on data corresponding to an integrated luminosity of 16.1 fb
−1
from proton-proton collisions at
s
=
13
TeV collected by the CMS experiment at the LHC in 2016. The dark quark is charged only under a new quantum-chromodynamics-like force, and forms an “emerging jet” via a parton shower, containing long-lived dark hadrons that give rise to displaced vertices when decaying to standard model hadrons. The data are consistent with the expectation from standard model processes. Limits are set at 95% confidence level excluding dark pion decay lengths between 5 and 225 mm for dark mediators with masses between 400 and 1250 GeV. Decay lengths smaller than 5 and greater than 225 mm are also excluded in the lower part of this mass range. The dependence of the limit on the dark pion mass is weak for masses between 1 and 10 GeV. This analysis is the first dedicated search for the pair production of a new particle that decays to a jet and an emerging jet.
We investigate the mechanical response of Zr$_{50}$Cu$_{40}$Al$_{10}$ and Zr$_{60}$Cu$_{30}$Al$_{10}$ metallic glasses under laser shock compression to reproduce hypervelocity impact conditions such ...as high longitudinal stresses and high strain rates in an unknown range of 10$^6$−10$^7$s$^{−1}$. Hugoniot curves and strength parameters (spall strength and strain rate) are obtained from free surface velocity profiles and compared with previous studies on the mechanical behaviour of Zr-based metallic glasses under plate impact experiments. We established Hugoniot curves for both compositions up to 100 GPa, corresponding to a particle velocity of 1.8 km/s, and consistent with literature up to 75 GPa. Concerning the strength parameters, we studied the evolution of the spall strength with the strain rate and obtained data unreached up to now from 1.7×10$^6$s$^{−1}$ to 2.7×10$^7$s$^{−1}$. This range of data correspond to strain rates of hypervelocity impacts of small debris (≈0.1−1mm) on space infrastructure shields. Moreover, we highlight a strong dependency of the spall strength with the strain rate starting from 2×10$^6$s$^{−1}$. Indeed, the spall strength increases from 2.6 GPa, close to its quasi-static tensile strength value, up to 13.6 GPa.
A
bstract
We compute the one-loop matching between the Standard Model Effective Field Theory and the low-energy effective field theory below the electroweak scale, where the heavy gauge bosons, the ...Higgs particle, and the top quark are integrated out. The complete set of matching equations is derived including effects up to dimension six in the power counting of both theories. We present the results for general flavor structures and include both the
C P
-even and
C P
-odd sectors. The matching equations express the masses, gauge couplings, as well as the coefficients of dipole, three-gluon, and four-fermion operators in the low-energy theory in terms of the parameters of the Standard Model Effective Field Theory. Using momentum insertion, we also obtain the matching for the
C P
-violating theta angles. Our results provide an ingredient for a model-independent analysis of constraints on physics beyond the Standard Model. They can be used for fixed- order calculations at one-loop accuracy and represent a first step towards a systematic next-to-leading-log analysis.
CMOS-compatible, refractory conductors are emerging as the materials that will advance novel concepts into real, practical plasmonic technologies. From the available pallet of materials, those with ...negative real permittivity at very short wavelengths are extremely rare; importantly, they are vulnerable to oxidationupon exposure to far-UV radiationand nonrefractory. Epitaxial, substoichiometric, cubic MoN (B1-MoN x ) films exhibit resistivity as low as 250 μΩ cm and negative real permittivity for experimental wavelengths as short as 155 nm, accompanied with unparalleled chemical and thermal stabilities, which are reported herein. Finite-difference time domain calculations suggest that B1-MoN x operates as an active plasmonic element deeper in the UV (100–200 nm) than any other known material, apart from Al, while being by far more stable and abundant than any other UV plasmonic conductor. Unexpectedly, the unique optical performance of B1-MoN x is promoted by nitrogen vacancies, thus changing the common perception on the role of defects in plasmonic materials.
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