On September 14th 2015 the first gravitational wave signal has been detected by the Advanced LIGO interferometers, opening the era of the gravitational astronomy and giving new opportunities to ...investigate the universe. The Advanced LIGO and Advanced Virgo interferometers are now back in a commissioning phase in order to improve their sensitivity for the next observing run, which will start in the first months of 2019. In the high-frequencies region of their sensitivity band, the detectors are shot-noise limited: the sensitivity in this frequency window could be improved increasing the laser input power, but this increases also the optical aberrations due to the thermal effects. The optical power absorptions in the substrate and coatings of the optics induce both an increase of the optical path length in the substrates of the mirrors (thermal lensing) and a thermal expansion of the optic itself along the optical axis (thermo-elastic deformation). Both these aberrations reduce the sensitivity of the detector, limiting its performances. In order to face and minimize them, an adaptive Thermal Compensation System is required in order to guarantee the proper operation of the interferometer. An overview of the present Thermal Compensation System system installed on Advanced Virgo, with also a focus on the possible improvements of the actual actuators for the next generation of detectors, is presented here.
We have recently experimentally demonstrated, for the first time, the activation of long-range attractive electrodynamic forces between proteins by means of THz spectroscopies, supported by ...fluorescence cross correlation spectroscopy and numerical simulations. Our experimental work provides a proof of principle of out-of-equilibrium collective oscillations activation of dipole-dipole electrodynamic intermolecular forces. It paves the way for exploring the potential role of electrodynamic intermolecular forces in living matter.
Motivated by the recent hints of lepton flavour non-universality in
B
-meson semi-leptonic decays, we study the constraints of perturbative unitarity on the new physics interpretation of the ...anomalies in
b
→
c
ℓ
ν
¯
and
b
→
s
ℓ
ℓ
¯
transitions. Within an effective field theory approach we find that
2
→
2
fermion scattering amplitudes saturate the unitarity bound below 9 and 80 TeV, respectively for
b
→
c
ℓ
ν
¯
and
b
→
s
ℓ
ℓ
¯
transitions. Stronger bounds, up to few TeV, are obtained when the leading effective operators are oriented in the direction of the third generation, as suggested by flavour models. We finally address unitarity constraints on simplified models explaining the anomalies and show that the new physics interpretation is ruled out in a class of perturbative realizations.
A
bstract
We attempt to explain recent anomalies in semileptonic
B
decays at LHCb via a composite Higgs model, in which both the Higgs and an SU(2)
L
-triplet leptoquark arise as pseudo-Goldstone ...bosons of the strong dynamics. Fermion masses are assumed to be generated via the mechanism of partial compositeness, which largely determines the leptoquark couplings and implies non-universal lepton interactions. The latter are needed to accommodate tensions in the
b
→
sμμ
dataset and to be consistent with a discrepancy measured at LHCb in the ratio of
B
+
→
K
+
μ
+
μ
−
to
B
+
→
K
+
e
+
e
−
branching ratios. The data imply that the leptoquark should have a mass of around a TeV. We find that the model is not in conflict with current flavour or direct production bounds, but we identify a few observables for which the new physics contributions are close to current limits and where the leptoquark is likely to show up in future measurements. The leptoquark will be pair-produced at the LHC and decay predominantly to third-generation quarks and leptons, and LHC13 searches will provide further strong bounds.
Advanced Virgo is the European gravitational-wave detector that, along with the American ones, is part of the global network of detectors that have been pinpointing gravitational waves since 2015. ...These kilometer-scale laser interferometers, measuring the distance between quasi-free-falling mirrors, represent the suitable detectors to explore the Universe through gravitational radiation. The initial Virgo experiment completed several runs of scientific data between 2007 and 2011, establishing the upper limits on the gravitational-wave rate expected for several astrophysical sources. The Advanced Virgo project led this instrument to unprecedented sensitivities making gravitational wave detections a routine occurrence. In this review, the basic techniques to build gravitational-waves interferometers and the upgrades needed to boost their sensitivities, even beyond the classical limit, are presented. The particular case of Advanced Virgo will be described hinting at its future developments, as well.
A
bstract
We propose a mechanism that allows for sizeable flavour violation in quark-lepton currents, while suppressing flavour changing neutral currents in quark-quark and lepton-lepton sectors. The ...mechanism is applied to the recently proposed “4321” renormalizable model, which can accommodate the current experimental anomalies in
B
-meson decays, both in charged and neutral currents, while remaining consistent with all other indirect flavour and electroweak precision measurements and direct searches at high-
p
T
. To support this claim, we present an exhaustive phenomenological survey of this fully calculable UV complete model and highlight the rich complementarity between indirect and direct searches.
A
bstract
While the
S
3
scalar leptoquark presents a possible tree-level explanation of the
b → sℓℓ
flavour anomalies, it suffers from two conceptual problems which are often disregarded by ...model-builders. Firstly, the quantum numbers of the
S
3
allow for a renormalisable diquark operator that would trigger rapid proton decay unless its coupling were tuned away. Secondly, one expects the leptoquark to have generic couplings to leptons, which require tuning to avoid stringent experimental bounds on lepton flavour violation. By gauging a U(1) current that acts as
L
μ
− L
τ
on the Standard Model (SM) fermions, and under which the leptoquark has charge
−
1, one can remedy both these problems. The additional U(1), which is spontaneously broken at some high scale, is associated with a massive
Z′
gauge boson and a scalar SM singlet Φ, which play no direct role in mediating the anomalous
B
meson decays. By computing one- and two-loop mass corrections, we show that this pair of particles can be hidden away at much higher mass scales without destabilising either the Higgs or the leptoquark masses. The only low-energy relic of gauging
L
μ
− L
τ
is thus the accidental global symmetry structure of the lagrangian. On the other hand, we find quite generally that an
S
3
leptoquark that mediates the
b → sℓℓ
anomalies cannot be much heavier than a few TeV without itself inducing large Higgs mass corrections.
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