131 research outputs found
Flavour and polarisation in heavy neutrino production at e+ e- colliders
We analyse l W nu production at ILC, paying special attention to the role of
the final lepton flavour and beam polarisation in the search for a new heavy
neutrino N. We show that a sizeable coupling to the electron V_eN ~ 10^-2 is
necessary to have an observable signal in any of the channels, despite the fact
that the signal may be more visible in muon or tau final states. The
non-observation of a heavy neutrino at ILC will improve the present upper bound
on its mixing with the electron by more than one order of magnitude, V_eN <
0.007 for m_N between 200 and 400 GeV.Comment: 17 pages, 5 PS figures. References added. To be published in PL
Model-Independent Searches for New Quarks at the LHC
New vector-like quarks can have sizable couplings to first generation quarks
without conflicting with current experimental constraints. The coupling with
valence quarks and unique kinematics make single production the optimal
discovery process. We perform a model-independent analysis of the discovery
reach at the Large Hadron Collider for new vector-like quarks considering
single production and subsequent decays via electroweak interactions. An early
LHC run with 7 TeV center of mass energy and 1 fb-1 of integrated luminosity
can probe heavy quark masses up to 1 TeV and can be competitive with the
Tevatron reach of 10 fb-1. The LHC with 14 TeV center of mass energy and 100
fb-1 of integrated luminosity can probe heavy quark masses up to 3.7 TeV for
order one couplings.Comment: 37 pages, 11 figures, 7 table
A heterometallic [LnLn′Ln] lanthanide complex as a qubit with embedded quantum error correction
We show that a [Er-Ce-Er] molecular trinuclear coordination compound is a promising platform to implement the three-qubit quantum error correction code protecting against pure dephasing, the most important error in magnetic molecules. We characterize it by preparing the [Lu-Ce-Lu] and [Er-La-Er] analogues, which contain only one of the two types of qubit, and by combining magnetometry, low-temperature specific heat and electron paramagnetic resonance measurements on both the elementary constituents and the trimer. Using the resulting parameters, we demonstrate by numerical simulations that the proposed molecular device can efficiently suppress pure dephasing of the spin qubits
Subtle alterations in cerebrovascular reactivity in mild cognitive impairment detected by graph theoretical analysis and not by the standard approach.
There is growing support that cerebrovascular reactivity (CVR) in response to a vasodilatory challenge, also defined as the cerebrovascular reserve, is reduced in Alzheimer's disease dementia. However, this is less clear in patients with mild cognitive impairment (MCI). The current standard analysis may not reflect subtle abnormalities in CVR. In this study, we aimed to investigate vasodilatory-induced changes in the topology of the cerebral blood flow correlation (CBF javax.xml.bind.JAXBElement@6894b36 ) network to study possible network-related CVR abnormalities in MCI. For this purpose, four CBF javax.xml.bind.JAXBElement@389286d6 networks were constructed: two using CBF SPECT data at baseline and under the vasodilatory challenge of acetazolamide (ACZ), obtained from a group of 26 MCI patients; and two equivalent networks from a group of 26 matched cognitively normal controls. The mean strength of association ( javax.xml.bind.JAXBElement@58a7138c ) and clustering coefficient ( javax.xml.bind.JAXBElement@5f56d60d ) were used to evaluate ACZ-induced changes on the topology of CBF javax.xml.bind.JAXBElement@13cae62a networks. We found that cognitively normal adults and MCI patients show different patterns of javax.xml.bind.JAXBElement@3fc266b3 and javax.xml.bind.JAXBElement@5f9929b4 changes. The observed differences included the medial prefrontal cortices and inferior parietal lobe, which represent areas involved in MCI's cognitive dysfunction. In contrast, no substantial differences were detected by standard CVR analysis. These results suggest that graph theoretical analysis of ACZ-induced changes in the topology of the CBF javax.xml.bind.JAXBElement@36167af4 networks allows the identification of subtle network-related CVR alterations in MCI, which couldn't be detected by the standard approach
CP Violation and Family Mixing in the Effective Electroweak Lagrangian
We construct the most general effective Lagrangian of the matter sector of
the Standard Model, including mixing and CP violating terms. The Lagrangian
contains the effective operators that give the leading contribution in theories
where the physics beyond the Standard Model shows at a scale .
We perform the diagonalization and passage to the physical basis in full
generality. We determine the contribution to the different observables and
discuss the possible new sources of CP violation, the idea being to be able to
gain some knowledge about new physics beyond the Standard Model from general
considerations, without having to compute model by model. The values of the
coefficients of the effective Lagrangian in some theories, including the
Standard Model, are presented and we try to draw some general conclusions about
the general pattern exhibited by physics beyond the Standard Model in what
concerns CP violation. In the process we have had to deal with two theoretical
problems which are very interesting in their own: the renormalization of the
CKM matrix elements and the wave function renormalization in the on-shell
scheme when mixing is present.Comment: A misplaced sentence was correcte
Bounds for Lepton Flavor Violation and the Pseudoscalar Higgs in the General Two Higgs Doublet Model using muon factor
Current experimental data from the muon factor, seems to show the
necessity of physics beyond the Standard Model (SM), since the difference
between SM and experimental predictions is 2.6. In the framework of
the General Two Higgs Doublet Model (2HDM), we calculate the muon anomalous
magnetic moment to get lower and upper bounds for the Flavour Changing (FC)
Yukawa couplings in the leptonic sector. We also obtain lower bounds for the
mass of the pseudoscalar Higgs () as a function of the parameters of
the model.Comment: 12 pages, RevTex4, 5 figures. Improved presentation, updated
experimental data, amplified analysis, new figures added. Subbmited to Phys.
Rev.
Lepton Flavor Violation in the Two Higgs Doublet Model type III
We consider the Two Higgs Doublet Model (2HDM) of type III which leads to
Flavour Changing Neutral Currents (FCNC) at tree level in the leptonic sector.
In the framework of this model we can have, in principle, two situations: the
case (a) when both doublets acquire a vacuum expectation value different from
zero and the case (b) when only one of them is not zero. In addition, we show
that we can make two types of rotations for the flavor mixing matrices which
generates four types of lagrangians, with the rotation of type I we recover the
case (b) from the case (a) in the limit , and with the
rotation of type II we obtain the case (b) from (a) in the limit Moreover, two of the four possible lagrangians correspond to the models
of types I and II plus Flavor Changing (FC) interactions. The analitical
expressions of the partial lepton number violating widths and are derived for the cases (a) and (b) and both
types of rotations.In all cases these widths go asymptotically to zero in
the decoupling limit for all Higgses. We present from our analysis upper bounds
for the flavour changing transition and we show that such bounds
are sensitive to the VEV structure and the type of rotation utilized.Comment: 7 pages RevTeX4, 4 figures postscript, new section added and some new
reference
Non-standard interactions versus non-unitary lepton flavor mixing at a neutrino factory
The impact of heavy mediators on neutrino oscillations is typically described
by non-standard four-fermion interactions (NSIs) or non-unitarity (NU). We
focus on leptonic dimension-six effective operators which do not produce
charged lepton flavor violation. These operators lead to particular
correlations among neutrino production, propagation, and detection non-standard
effects. We point out that these NSIs and NU phenomenologically lead, in fact,
to very similar effects for a neutrino factory, for completely different
fundamental reasons. We discuss how the parameters and probabilities are
related in this case, and compare the sensitivities. We demonstrate that the
NSIs and NU can, in principle, be distinguished for large enough effects at the
example of non-standard effects in the --sector, which basically
corresponds to differentiating between scalars and fermions as heavy mediators
as leading order effect. However, we find that a near detector at superbeams
could provide very synergistic information, since the correlation between
source and matter NSIs is broken for hadronic neutrino production, while NU is
a fundamental effect present at any experiment.Comment: 32 pages, 5 figures. Final version published in JHEP. v3: Typo in Eq.
(27) correcte
Factors Associated with Mortality in Patients with COVID-19 from a Hospital in Northern Peru
We aimed to identify the factors associated with mortality in patients with COVID-19 from the hospitalization service of the Cayetano Heredia Hospital, Piura, Peru, from May to June 2020. A prospective study was conducted in hospitalized patients with a confirmed diagnosis of COVID-19 through serological and/or molecular reactive testing. The dependent variable was death due to COVID-19, and the independent variables were the epidemiological, clinical and laboratory characteristics of the patient. The chi-square test and the non-parametric Mann–Whitney U test were used, with a significance level of 5%. Of 301 patients with COVID-19, the majority of them were male (66.1%), and the mean age was 58.63 years. Of the patients analyzed, 41.3% of them died, 40.2% of them were obese and 59.8% of them had hepatic steatosis. The three most frequent signs/symptoms were dyspnea (90.03%), fatigue (90.03%) and a cough (84.72%). Being an older adult (p = 0.011), being hospitalized in the ICU (p = 0.001), overweight (p = 0.016), obese (p = 0.021) and having compromised consciousness (p = 0.039) and thrombocytopenia (p = 0.024) were associated with mortality due to COVID-19. Overall, the mortality rate due to COVID-19 was 41.3%. Having an older age, being hospitalized in the ICU, overweight, obese and having compromised consciousness and thrombocytopenia were positively associated with mortality in patients with COVID-19. These findings highlight the need to establish an adequate system of surveillance and epidemiological education in hospitals and communities in the event of new outbreaks, especially in rural and northern Peru
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