Spin Coulomb drag in the two-dimensional electron liquid

We calculate the spin-drag transresistivity $\rho_{\uparrow \downarrow}(T)$ in a two-dimensional electron gas at temperature $T$ in the random phase approximation. In the low-temperature regime we show that, at variance with the three-dimensional low-temperature result [$\rho_{\uparrow\downarrow}(T) \sim T^2$], the spin transresistivity of a two-dimensional {\it spin unpolarized} electron gas has the form $\rho_{\uparrow\downarrow}(T) \sim T^2 \ln T$. In the spin-polarized case the familiar form $\rho_{\uparrow\downarrow}(T) =A T^2$ is recovered, but the constant of proportionality $A$ diverges logarithmically as the spin-polarization tends to zero. In the high-temperature regime we obtain $\rho_{\uparrow \downarrow}(T) = -(\hbar / e^2) (\pi^2 Ry^* /k_B T)$ (where $Ry^*$ is the effective Rydberg energy) {\it independent} of the density. Again, this differs from the three-dimensional result, which has a logarithmic dependence on the density. Two important differences between the spin-drag transresistivity and the ordinary Coulomb drag transresistivity are pointed out: (i) The $\ln T$ singularity at low temperature is smaller, in the Coulomb drag case, by a factor $e^{-4 k_Fd}$ where $k_F$ is the Fermi wave vector and $d$ is the separation between the layers. (ii) The collective mode contribution to the spin-drag transresistivity is negligible at all temperatures. Moreover the spin drag effect is, for comparable parameters, larger than the ordinary Coulomb drag effect.Comment: 6 figures; various changes; version accepted for publicatio

Parkin isoforms expression in lung adenocarcinoma

PARK2, also known as parkin, is a gene mutated in autosomal recessive juvenile parkinsonism and it has been shown to exhibit E3 ubiquitin ligase activity. However it seems to fulfill also a wide spectrum of protective functions. Recent studies have demonstrated that parkin is an important regulator of process that maintain mitochondrial quality and it is also implicated in proteasomal degradation of toxic substrates. This gene has been also shown to be genetically altered and/or aberrantly expressed in a wide variety of human cancers including lung cancer (Cesari et al., 2003; Veeriah S. et al., 2010). Although many alternatively spliced isoforms have been identified, until now studies have been focused on the full-length isoform (D’Agata and Cavallaro, 2004). To characterize the role of parkin isoforms in lung tumorigenesis we analyzed their expression pattern in human lung adenocarcinomas. These data were correlated to their expression pattern either in human lung epithelial carcinoma (A549) or in human normal bronchial epithelial (BEAS-2B) cell lines. Western blot and immunofluorescence analyses were performed by using two antibodies recognizing different domains of the full length protein. Immunoblots showed that lung adenocarcinomas express parkin isoforms of 50, 37 and 20 kDa. Their expressions were significantly increased in A549 as compared to BEAS-2B, suggesting that parkin isoforms might be involved in cancer progression. In order to characterize some functions of these isoforms, both cell lines were cultured in complete medium or serum starved medium and treated with the proteasome inhibitor MG132 or with carbonyl cyanide 3- clorophenylhydrazone (CCCP), a uncoupling agent that dissipates the mitochondrial membrane. Data obtained revealed that each treatment affects pattern expression of parkin isoforms. These results suggest that some parkin isoforms might be molecular markers of lung adenocarcinoma

Parkin isoforms expression in gliomas

Parkin (PARK2) is one of the largest genes in the human genome encoding for an E3 ubiquitin ligase. Its mutation is the cause of early-onset Parkinson’s disease, but recently it is linked to other pathologies including cancer. Parkin acts as a tumor suppressor. It displays a wide neuroprotective activity by promoting the removal of damaged mitochondria via mitophagy and increasing proteasomal degradation of toxic substrates. PARK2 primary transcript undergoes to an extensive alternative splicing, which enhances transcriptomic diversification and protein diversity in tissues and cells. To date, GenBank lists 26 human PARK2 transcripts corresponding to 21 different alternative splice variants. These transcripts show different expression patterns and encode for proteins with different functions, molecular weight and isoelectric point. Previous studies identified inactivating somatic mutations and frequent intragenic deletions of PARK2 in human cancers including gliomas (Veeriah et al., 2010). Recently, it has been demonstrated that Parkin pathway activation is predictive for the survival outcome of patients with glioma (Yeo et al., 2012). However, these papers focused on the expression of full length Parkin. In the present work we analyzed the expression pattern of Parkin isoforms in astrocytomas of different grade and we investigated their functions in a human glioblastoma multiforme cell line. Immunoblotting analysis by using two specific antibodies revealed that Parkin expression is generally higher in malignant glioblastoma than in less invasive astrocytomas, indicating a correlation between expression pattern of Parkin isoforms and tumor malignancy. Serum deprivation or treatment with a proteosome inhibitor MG132 or with carbonyl cyanide 3-chlorophenylhydrazone (CCCP), an uncoupling agent that dissipates the cells mitochondrial membrane potential, increased expression of 100-55-50 kDa parkin isoforms in glioma cells as compared to controls. These results, consistent with other studies, demonstrated a functional connection between Parkin expression, mitochondrial integrity and endoplasmic reticulum stress (Bouman et al., 2011). Parkin isoforms expression was also confirmed by confocal microscopy analysis. These results suggest that the characterization of some PARK2 isoforms may be usefull clinically to develop a prognostic tool in patients with brain tumor

Measurement of Two-Qubit States by a Two-Island Single Electron Transistor

We solve the master equations of two charged qubits measured by a single-electron transistor (SET) consisted of two islands. We show that in the sequential tunneling regime the SET current can be used for reading out results of quantum calculations and providing evidences of two-qubit entanglement, especially when the interaction between the two qubits is weak

Measurement of fiducial and differential W + W - production cross-sections at s = 13 TeV with the ATLAS detector

Abstract: A measurement of fiducial and differential cross-sections for W+W- production in proton–proton collisions at s=13 TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 36.1 fb-1 is presented. Events with one electron and one muon are selected, corresponding to the decay of the diboson system as WW→e±νμ∓ν. To suppress top-quark background, events containing jets with a transverse momentum exceeding 35 GeV are not included in the measurement phase space. The fiducial cross-section, six differential distributions and the cross-section as a function of the jet-veto transverse momentum threshold are measured and compared with several theoretical predictions. Constraints on anomalous electroweak gauge boson self-interactions are also presented in the framework of a dimension-six effective field theory

Identification of boosted Higgs bosons decaying into b -quark pairs with the ATLAS detector at 13 TeV

Abstract: This paper describes a study of techniques for identifying Higgs bosons at high transverse momenta decaying into bottom-quark pairs, H→bb¯, for proton–proton collision data collected by the ATLAS detector at the Large Hadron Collider at a centre-of-mass energy s=13 TeV. These decays are reconstructed from calorimeter jets found with the anti-ktR=1.0 jet algorithm. To tag Higgs bosons, a combination of requirements is used: b-tagging of R=0.2 track-jets matched to the large-R calorimeter jet, and requirements on the jet mass and other jet substructure variables. The Higgs boson tagging efficiency and corresponding multijet and hadronic top-quark background rejections are evaluated using Monte Carlo simulation. Several benchmark tagging selections are defined for different signal efficiency targets. The modelling of the relevant input distributions used to tag Higgs bosons is studied in 36 fb-1 of data collected in 2015 and 2016 using g→bb¯ and Z(→bb¯)γ event selections in data. Both processes are found to be well modelled within the statistical and systematic uncertainties

Search for non-resonant Higgs boson pair production in final states with leptons, taus, and photons in pp collisions at √s = 13 TeV with the ATLAS detector

A search is presented for non-resonant Higgs boson pair production, targeting the bbZZ, 4V (V = W or Z), V V τ τ , 4τ , γγV V and γγτ τ decay channels. Events are categorised based on the multiplicity of light charged leptons (electrons or muons), hadronically decaying tau leptons, and photons. The search is based on a data sample of proton-proton collisions at √s = 13 TeV recorded with the ATLAS detector during Run 2 of the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb−1. No evidence of the signal is found and the observed (expected) upper limit on the cross-section for non-resonant Higgs boson pair production is determined to be 17 (11) times the Standard Model predicted cross-section at 95% confidence level under the background-only hypothesis. The observed (expected) constraints on the HHH coupling modifier, κλ, are determined to be −6.2 < κλ < 11.6 (−4.5 < κλ < 9.6) at 95% confidence level, assuming the Standard Model for the expected limits and that new physics would only affect κλ

Search for single production of vector-like T quarks decaying into Ht or Zt in pp collisions at s√ = 13 TeV with the ATLAS detector

This paper describes a search for the single production of an up-type vector-like quark (T) decaying as T → Ht or T → Zt. The search utilises a dataset of pp collisions at s√ = 13 TeV collected with the ATLAS detector during the 2015–2018 data-taking period of the Large Hadron Collider, corresponding to an integrated luminosity of 139 fb−1. Data are analysed in final states containing a single lepton with multiple jets and b-jets. The presence of boosted heavy resonances in the event is exploited to discriminate the signal from the Standard Model background. No significant excess above the Standard Model expectation is observed, and 95% CL upper limits are set on the production cross section of T quarks in different decay channels. The results are interpreted in several benchmark scenarios to set limits on the mass and universal coupling strength (κ) of the vector-like quark. For singlet T quarks, κ values above 0.53 are excluded for all masses below 2.3 TeV. At a mass of 1.6 TeV, κ values as low as 0.35 are excluded. For T quarks in the doublet scenario, where the production cross section is much lower, κ values above 0.72 are excluded for all masses below 1.7 TeV, and this exclusion is extended to κ above 0.55 for low masses around 1.0 TeV

Search for excited τ-leptons and leptoquarks in the final state with τ-leptons and jets in pp collisions at s√ = 13 TeV with the ATLAS detector

A search is reported for excited τ-leptons and leptoquarks in events with two hadronically decaying τ-leptons and two or more jets. The search uses proton-proton (pp) collision data at s√ = 13 TeV recorded by the ATLAS experiment during the Run 2 of the Large Hadron Collider in 2015–2018. The total integrated luminosity is 139 fb−1. The excited τ-lepton is assumed to be produced and to decay via a four-fermion contact interaction into an ordinary τ-lepton and a quark-antiquark pair. The leptoquarks are assumed to be produced in pairs via the strong interaction, and each leptoquark is assumed to couple to a charm or lighter quark and a τ-lepton. No excess over the background prediction is observed. Excited τ-leptons with masses below 2.8 TeV are excluded at 95% CL in scenarios with the contact interaction scale Λ set to 10 TeV. At the extreme limit of model validity where Λ is set equal to the excited τ-lepton mass, excited τ-leptons with masses below 4.6 TeV are excluded. Leptoquarks with masses below 1.3 TeV are excluded at 95% CL if their branching ratio to a charm quark and a τ-lepton equals 1. The analysis does not exploit flavour-tagging in the signal region

Measurements of the production cross-section for a Z boson in association with b- or c-jets in proton–proton collisions at √s = 13 TeV with the ATLAS detector

This paper presents a measurement of the production cross-section of a Z boson in association with bor c-jets, in proton–proton collisions at √s = 13 TeV with the ATLAS experiment at the Large Hadron Collider using data corresponding to an integrated luminosity of 140 fb−1. Inclusive and differential cross-sections are measured for events containing a Z boson decaying into electrons or muons and produced in association with at least one b-jet, at least one c-jet, or at least two b-jets with transverse momentum pT > 20 GeV and rapidity |y| < 2.5. Predictions from several Monte Carlo generators based on next-to-leading-order matrix elements interfaced with a parton-shower simulation, with different choices of flavour schemes for initial-state partons, are compared with the measured cross-sections. The results are also compared with novel predictions, based on infrared and collinear safe jet flavour dressing algorithms. Selected Z+ ≥ 1 c-jet observables, optimized for sensitivity to intrinsic-charm, are compared with benchmark models with different intrinsic-charm fractions