A
bstract
In order to simultaneously account for both
R
D
(
∗
)
and
R
K
(
∗
)
anomalies in
B
-decays, we consider an extension of the Standard Model by a single vector leptoquark field, and study how ...one can achieve the required lepton flavour non-universality, starting from a priori universal gauge couplings. While the unitary quark-lepton mixing induced by SU(2)
L
breaking is insufficient, we find that effectively nonunitary mixings hold the key to simultaneously address the
R
K
(
∗
)
and
R
D
(
∗
) anomalies. As an intermediate step towards various UV-complete models, we show that the mixings of charged leptons with additional vector-like heavy leptons successfully provide a nonunitary framework to explain
R
K
(
∗
)
and
R
D
(
∗
)
. These realisations have a strong impact for electroweak precision observables and for flavour violating ones: isosinglet heavy lepton realisations are already excluded due to excessive contributions to lepton flavour violating
Z
-decays. Furthermore, in the near future, the expected progress in the sensitivity of charged lepton flavour violation experiments should allow to fully probe this class of vector leptoquark models.
A
bstract
A future high-luminosity
Z
-factory will offer the possibility to study rare
Z
decays, as those leading to lepton flavour violating final states. Processes such as
Z
→
ℓ
1
∓
ℓ
2
±
are ...potentially complementary to low-energy (high-intensity) observables of lepton flavour violation. In this work we address the impact of new sterile fermions on lepton flavour violating
Z
decays, focusing on potential searches at FCC-ee (TLEP), and taking into account experimental and observational constraints on the sterile states. We consider a minimal extension of the Standard Model by one sterile fermion state, and two well-motivated frameworks of neutrino mass generation, the Inverse Seesaw embedded into the Standard Model, and the
ν
MSM. Our study shows that sterile neutrinos can give rise to contributions to BR(
Z
→
ℓ
1
∓
ℓ
2
±
) within reach of the FCC-ee. We also discuss the complementarity between a high-luminosity
Z
-factory and low-energy charged lepton flavour violation facilities.
Flavour and CP symmetries in the inverse seesaw Hagedorn, C.; Kriewald, J.; Orloff, J. ...
The European physical journal. C, Particles and fields,
03/2022, Letnik:
82, Številka:
3
Journal Article
Recenzirano
Odprti dostop
We consider an inverse seesaw mechanism of neutrino mass generation in which the Standard Model is extended by
3
+
3
(heavy) sterile states, and endowed with a flavour symmetry
G
f
,
G
f
=
Δ
(
3
n
2
...)
or
G
f
=
Δ
(
6
n
2
)
, and a CP symmetry. These symmetries are broken in a peculiar way, so that in the charged lepton sector a residual symmetry
G
ℓ
is preserved, while the neutral fermion sector remains invariant under the residual symmetry
G
ν
=
Z
2
×
C
P
. We study the concrete setup, where the Majorana mass term for three of the sterile states conserves
G
ν
, while the remaining mass terms (i.e. couplings of left-handed leptons and heavy sterile states, as well as the Dirac-type couplings among the latter) do not break the flavour or CP symmetry. We perform a comprehensive analysis of lepton mixing for different classes of residual symmetries, giving examples for each of these, and study in detail the impact of the additional sterile states on the predictions for lepton mixing. We further confront our results with those obtained in the model-independent scenario, in which the light neutrino mass matrix leaves the residual symmetry
G
ν
intact. We consider the phenomenological impact of the inverse seesaw mechanism endowed with flavour and CP symmetries, in particular concerning effects of non-unitarity of the lepton mixing matrix (which strongly constrain the parameter space of the scenario), prospects for neutrinoless double beta decay and for charged lepton flavour violating processes.
The apparent tensions emerging from the comparison of experimental data of the anomalous magnetic moments of the muon and electron to the Standard Model predictions (
Δ
a
μ
,
e
) could be interpreted ...as a potential signal of New Physics. Models encompassing a light vector boson have been known to offer a satisfactory explanation to
Δ
a
μ
, albeit subject to stringent experimental constraints. Here we explore a minimal extension of the Standard Model via a leptophilic vector boson
Z
′
, under the hypothesis of strictly flavour-violating couplings of the latter to leptons. The most constraining observables to this ad-hoc construction emerge from lepton flavour universality violation (in
Z
and
τ
decays) and from rare charged lepton flavour violating transitions. Once these are accommodated, one can saturate the tensions in
Δ
a
μ
, but
Δ
a
e
is predicted to be Standard Model-like. We infer prospects for several observables, including leptonic
Z
decays and several charged lepton flavour violating processes. We also discuss potential signatures of the considered
Z
′
at a future muon collider, emphasising the role of the
μ
+
μ
-
→
τ
+
τ
-
forward-backward asymmetry as a key probe of the model.
Motivated by the recent experimental progress on the
B
-meson decay anomalies (in particular the angular observables in
B
→
K
∗
μ
μ
), we rely on a simplified-model approach to study the prospects of ...vector leptoquarks in what concerns numerous flavour observables, identifying several promising decay modes which would allow to (indirectly) probe such an extension. Our findings suggest that the confirmation of the
B
-meson decay anomalies, in parallel with positive signals (at Belle II or LHCb) for
τ
→
ϕ
μ
,
B
(
s
)
-meson decays to
τ
+
τ
-
and
τ
+
μ
-
(
τ
+
e
-
) final states, as well as an observation of certain charged lepton flavour violation decays (at COMET or Mu2e), would contribute to strengthen the case for this scenario. We also illustrate how the evolution of the experimental determination of
R
D
(
∗
)
could be instrumental in falsifying an explanation of the anomalous
B
-meson decay data via a vector
V
1
leptoquark.
We revisit charged lepton flavour in-flight conversions, in which a beam of electrons or muons is directed onto a fixed target,
e
+
N
→
μ
+
N
,
e
+
N
→
τ
+
N
and
μ
+
N
→
τ
+
N
, focusing on elastic ...interactions with a nucleus
N
. After a general discussion of this observable, we carry a full phenomenological analysis in the framework of minimal Standard Model extensions via sterile neutrinos, with a strong emphasis on the rôle of the increasingly more stringent constraints arising from other (low-energy) charged lepton flavour-violation observables. Despite the potential interest of this observable, in particular in the light of certain upcoming facilities with the capability of very intense lepton beams, our study suggests that due to current bounds on three-body decays (
ℓ
i
→
3
ℓ
j
) and
μ
-
e
conversion in nuclei, the expected number of conversions in such a minimal framework is dramatically reduced. An experimental observation of such a conversion would thus signal the presence of another source of flavour violation, possibly at tree level.
A
bstract
Motivated by a simultaneous explanation of the apparent discrepancies in the light charged lepton anomalous magnetic dipole moments, and the anomalous internal pair creation in
8
Be nuclear ...transitions, we explore a simple New Physics model, based on an extension of the Standard Model gauge group by a U(1)
B−L
. The model further includes heavy vector-like fermion fields, as well as an extra scalar responsible for the low-scale breaking of U(1)
B−L
, which gives rise to a light
Z′
boson. The new fields and currents allow to explain the anomalous internal pair creation in
8
Be while being consistent with various experimental constraints. Interestingly, we find that the contributions of the
Z′
and the new U(1)
B−L
-breaking scalar can also successfully account for both (
g −
2)
e,μ
anomalies; the strong phenomenological constraints on the model’s parameter space ultimately render the combined explanation of (
g −
2)
e
and the anomalous internal pair creation in
8
Be particularly predictive. The underlying idea of this minimal “prototype model” can be readily incorporated into other protophobic U(1) extensions of the Standard Model.
Mortality is increased after a hip fracture, and strategies that improve outcomes are needed.
In this randomized, double-blind, placebo-controlled trial, 1065 patients were assigned to receive yearly ...intravenous zoledronic acid (at a dose of 5 mg), and 1062 patients were assigned to receive placebo. The infusions were first administered within 90 days after surgical repair of a hip fracture. All patients (mean age, 74.5 years) received supplemental vitamin D and calcium. The median follow-up was 1.9 years. The primary end point was a new clinical fracture.
The rates of any new clinical fracture were 8.6% in the zoledronic acid group and 13.9% in the placebo group, a 35% risk reduction with zoledronic acid (P=0.001); the respective rates of a new clinical vertebral fracture were 1.7% and 3.8% (P=0.02), and the respective rates of new nonvertebral fractures were 7.6% and 10.7% (P=0.03). In the safety analysis, 101 of 1054 patients in the zoledronic acid group (9.6%) and 141 of 1057 patients in the placebo group (13.3%) died, a reduction of 28% in deaths from any cause in the zoledronic acid group (P=0.01). The most frequent adverse events in patients receiving zoledronic acid were pyrexia, myalgia, and bone and musculoskeletal pain. No cases of osteonecrosis of the jaw were reported, and no adverse effects on the healing of fractures were noted. The rates of renal and cardiovascular adverse events, including atrial fibrillation and stroke, were similar in the two groups.
An annual infusion of zoledronic acid within 90 days after repair of a low-trauma hip fracture was associated with a reduction in the rate of new clinical fractures and with improved survival. (ClinicalTrials.gov number, NCT00046254 ClinicalTrials.gov.).
Importance Bleeding esophageal varices has been studied extensively, but bleeding gastric varices (BGV) has received much less investigation. However, BGV has been reported in ≤30% of patients with ...acute variceal bleeding. In our studies of 1,836 bleeding cirrhotics, 12.7% were bleeding from gastric varices. BGV mortality rate of 45–55% has been reported. The BGV literature has mainly involved retrospective case reports, often with short-term follow-up. Objective We sought to describe the results of a prospective, randomized, controlled trial (RCT) in unselected, consecutive patients with BGV comparing endoscopic therapy (ET) with portacaval shunt (PCS; n = 518), and later comparing emergency transjugular intrahepatic portosystemic shunt (TIPS) with emergency portacaval shunt (EPCS; n = 70). Design, setting, and participants Initially, our RCT involved 518 patients with BGV comparing ET with direct PCS regarding control of bleeding, mortality rate, and disability. When entry of patients ended, the RCT was expanded to compare emergency TIPS with EPCS ( n = 70). This RCT of BGV was separate from our other RCTs of bleeding esophageal varices. Interventions Initially, ET was compared with PCS. In the second part of our RCT, emergency TIPS was compared with emergency PCS (EPCS). Main outcome measures Outcomes were survival, control of bleeding, portal-systemic encephalopathy (PSE), quality of life, and direct costs of care. In the RCT of ET versus PCS, 28 and 30%, respectively, were in Child class C. In the expanded RCT of TIPS versus EPCS, 40 and 41%, respectively, were in Child class C. Permanent control of BGV was achieved in 97–100% of patients treated by emergency or elective PCS, compared with 27–29% by ET. TIPS was even less effective, achieving long-term control of BGV in only 6%. Survival rates after PCS were greater at all time intervals and in all Child classes ( P < .001). Repeated episodes of PSE occurred in 50% of TIPS patients, 16-17% treated by ET, and 8-11% treated by PCS. Shunt stenosis or occlusion occurred in 67% of TIPS patients, in contrast with 0–2% of PCS patients. Conclusion These results support the conclusion that PCS is uniformly effective, whereas ET and TIPS are not very effective.
A
bstract
We study the implications of the recent LHCb limit and results on
B
s
→
μ
+
μ
−
and
B
→
K
*
μ
+
μ
−
observables in the constrained SUSY scenarios. After discussing the Standard Model ...predictions and carefully estimating the theoretical errors, we show the constraining power of these observables in CMSSM and NUHM. The latest limit on BR(
B
s
→
μ
+
μ
−
), being very close to the SM prediction, constrains strongly the large tan
β
regime and we show that the various angular observables from
B
→
K
*
μ
+
μ
−
decay can provide complementary information in particular for intermediate tan
β
values.
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