A
bstract
We compute the generic one-loop contribution involving scalar leptoquarks (LQ) to the
W
and
Z
leptonic decay widths. In our computation we include for the first time the finite terms and ...the corrections due to the external momenta of the electroweak bosons, which is a step beyond the leading-logarithmic approximation considered in the literature so far. We show that the terms we include can be numerically quite significant. They amount to about 20% for scalar LQ masses below 1
.
5 TeV, as currently allowed by the direct searches at the LHC. To further illustrate the relevance of our results we revisit a model with two light scalar LQs, proposed to accommodate the
B
-physics anomalies. We show that the finite terms we computed can reduce the tension with the
Z
-pole data.
B cells are important in the pathogenesis of many, and perhaps all, immune-mediated diseases. Each B cell expresses a single B cell receptor (BCR)
, and the diverse range of BCRs expressed by the ...total B cell population of an individual is termed the 'BCR repertoire'. Our understanding of the BCR repertoire in the context of immune-mediated diseases is incomplete, and defining this could provide new insights into pathogenesis and therapy. Here, we compared the BCR repertoire in systemic lupus erythematosus, anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis, Crohn's disease, Behçet's disease, eosinophilic granulomatosis with polyangiitis, and immunoglobulin A (IgA) vasculitis by analysing BCR clonality, use of immunoglobulin heavy-chain variable region (IGHV) genes and-in particular-isotype use. An increase in clonality in systemic lupus erythematosus and Crohn's disease that was dominated by the IgA isotype, together with skewed use of the IGHV genes in these and other diseases, suggested a microbial contribution to pathogenesis. Different immunosuppressive treatments had specific and distinct effects on the repertoire; B cells that persisted after treatment with rituximab were predominately isotype-switched and clonally expanded, whereas the inverse was true for B cells that persisted after treatment with mycophenolate mofetil. Our comparative analysis of the BCR repertoire in immune-mediated disease reveals a complex B cell architecture, providing a platform for understanding pathological mechanisms and designing treatment strategies.
We present a global analysis of leptonic and semileptonic kaon decay data, including all recent results published by the BNL-E865, KLOE, KTeV, ISTRA+ and NA48 experiments. This analysis, in ...conjunction with precise lattice calculations of the hadronic matrix elements now available, leads to a very precise determination of |
V
us
| and allows us to perform several stringent tests of the Standard Model.
We present a lattice QCD determination of the chiral quark condensate based on a new method. We extract the quark condensate from the operator product expansion of the quark propagator at short ...euclidean distances, where it represents the leading contribution in the chiral limit. From this study we obtain \({\left\langle {\bar{q}q} \right\rangle }^{{\overline{{{\text{MS}}} }} {\left( {2\;{\text{GeV}}} \right)} = - {\left( {265 \pm 5 \pm 22\;{\text{MeV}}} \right)}^{3} \), in good agreement with determinations of this quantity based on different approaches. The simulation is performed by using the \({\cal O}(a)\)-improved Wilson action at\(\beta = 6.45\)on a volume 323 × 70 in the quenched approximation.
The axion shield Andrianov, A.; Espriu, D.; Mescia, F. ...
Physics letters. B,
02/2010, Letnik:
684, Številka:
2-3
Journal Article
Recenzirano
Odprti dostop
We investigate the propagation of a charged particle in a spatially constant, but time dependent, pseudoscalar background. Physically this pseudoscalar background could be provided by a relic axion ...density. The background leads to an explicit breaking of Lorentz invariance; as a consequence the process p→pγ is possible and the background acts as a shield against extremely energetic cosmic rays, an effect somewhat similar to the GZK cut-off effect. The effect is model independent and can be computed exactly. The hypothetical detection of the photons radiated via this mechanism would provide an indirect way of verifying the cosmological relevance of axions.
We present a quenched lattice study of the form factors
f
+
(
q
2
)
and
f
0
(
q
2
)
of the matrix elements
〈
π
|
s
¯
γ
μ
u
|
K
〉
. We focus on the second-order SU(3)-breaking quantity
1
−
f
+
(
0
)
..., which is necessary to extract
|
V
u
s
|
from
K
ℓ
3
decays. For this quantity we show that it is possible to reach the percent precision which is the required one for a significant determination of
|
V
u
s
|
. The leading quenched chiral logarithms are corrected for by using analytic calculations in quenched chiral perturbation theory. Our final result,
f
+
K
0
π
−
(
0
)
=
0.960
±
0.005
stat
±
0.007
syst
, where the systematic error does not include the residual quenched effects, is in good agreement with the estimate made by Leutwyler and Roos. A comparison with other non-lattice computations and the impact of our result on the extraction of
|
V
u
s
|
are also presented.
A
bstract
We present a complete and optimal set of observables for the exclusive 4-body
meson decay
(→
Kπ
)
ℓ
+
ℓ
−
in the low dilepton mass region, that contains a maximal number of clean ...observables. This basis of observables is built in a systematic way. We show that all the previously defined observables and any observable that one can construct, can be expressed as a function of this basis. This set of observables contains all the information that can be extracted from the angular distribution in the cleanest possible way. We provide explicit expressions for the full and the uniangular distributions in terms of this basis. The conclusions presented here can be easily extended to the large-
q
2
region. We study the sensitivity of the observables to right-handed currents and scalars. Finally, we present for the first time all the symmetries of the full distribution including massive terms and scalar contributions.
PDF
