Modeling Lepton-Nucleon Inelastic Scattering from High to Low Momentum Transfer

We present a model for inclusive charged lepton-nucleon and (anti)neutrino-nucleon cross sections at momentum transfer squared, $Q^2$, $\sim1 {\rm GeV}^2$. We quantify the impact of existing low-Q charged-lepton deep-inelastic scattering (DIS) data on effects due to high-twist operators and on the extraction of parton distribution functions (PDFs). No evidence is found for twist-6 contributions to structure functions (SF), and for a twist-4 term in the logitudinal SF at $x\gtrsim0.1$. We find that DIS data are consistent with the NNLO QCD approximation with the target mass and phenomenological high twist corrections. For $Q^2<1 {\rm GeV}^2$, we extend extrapolation of the operator product expansion, preserving the low-$Q$ current-conservation theorems. The procedure yields a good description of data down to $Q^2\sim 0.5 {\rm GeV}^2$. An updated set of PDFs with reduced uncertainty and applicable down to small momentum transfers in the lepton-nucleon scattering is obtained.Comment: 10 pages, 6 figures, proceedings of the 5th International Workshop on Neutrino-Nucleus Interactions in the Few-GeV Region (NuInt07), Batavia, Illinois, 30 May - 3 Jun 200

Single Pion production from Nuclei

We have studied charged current one pion production induced by $\nu_\mu(\bar\nu_\mu)$ from some nuclei. The calculations have been done for the incoherent pion production processes from these nuclear targets in the $\Delta$ dominance model and take into account the effect of Pauli blocking, Fermi motion and renormalization of $\Delta$ properties in the nuclear medium. The effect of final state interactions of pions has also been taken into account. The numerical results have been compared with the recent results from the MiniBooNE experiment for the charged current 1$\pi$ production, and also with some of the older experiments in Freon and Freon-Propane from CERN.Comment: 5 pages, 5 figures, 5th International Workshop on Neutrino-Nucleus Interactions in the few GeV region(NuInt07), Batavia, Illinois, 30May-3June, 200

Robust quantum coherence above the Fermi sea

In this paper we present an experiment where we measured the quantum coherence of a quasiparticle injected at a well-defined energy above the Fermi sea into the edge states of the integer quantum Hall regime. Electrons are introduced in an electronic Mach-Zehnder interferometer after passing through a quantum dot that plays the role of an energy filter. Measurements show that above a threshold injection energy, the visibility of the quantum interferences is almost independent of the energy. This is true even for high energies, up to 130~$\mu$eV, well above the thermal energy of the measured sample. This result is in strong contradiction with our theoretical predictions, which instead predict a continuous decrease of the interference visibility with increasing energy. This experiment raises serious questions concerning the understanding of excitations in the integer quantum Hall regime

Tomonaga-Luttinger physics in electronic quantum circuits

In one-dimensional conductors, interactions result in correlated electronic systems. At low energy, a hallmark signature of the so-called Tomonaga-Luttinger liquids (TLL) is the universal conductance curve predicted in presence of an impurity. A seemingly different topic is the quantum laws of electricity, when distinct quantum conductors are assembled in a circuit. In particular, the conductances are suppressed at low energy, a phenomenon called dynamical Coulomb blockade (DCB). Here we investigate the conductance of mesoscopic circuits constituted by a short single-channel quantum conductor in series with a resistance, and demonstrate a proposed link to TLL physics. We reformulate and establish experimentally a recently derived phenomenological expression for the conductance using a wide range of circuits, including carbon nanotube data obtained elsewhere. By confronting both conductance data and phenomenological expression with the universal TLL curve, we demonstrate experimentally the predicted mapping between DCB and the transport across a TLL with an impurity.Comment: 9p,6fig+SI; to be published in nature comm; v2: mapping extended to finite range interactions, added discussion and SI material, added reference

Strong back-action of a linear circuit on a single electronic quantum channel

What are the quantum laws of electricity in mesoscopic circuits? This very fundamental question has also direct implications for the quantum engineering of nanoelectronic devices. Indeed, when a quantum coherent conductor is inserted into a circuit, its transport properties are modified. In particular, its conductance is reduced because of the circuit back-action. This phenomenon, called environmental Coulomb blockade, results from the granularity of charge transfers across the coherent conductor. Although extensively studied for a tunnel junction in a linear circuit, it is only fully understood for arbitrary short coherent conductors in the limit of small circuit impedances and small conductance reduction. Here, we investigate experimentally the strong back-action regime, with a conductance reduction of up to 90%. This is achieved by embedding a single quantum channel of tunable transmission in an adjustable on-chip circuit of impedance comparable to the resistance quantum $R_K=h/e^2$ at microwave frequencies. The experiment reveals important deviations from calculations performed in the weak back-action framework, and matches with recent theoretical results. From these measurements, we propose a generalized expression for the conductance of an arbitrary quantum channel embedded in a linear circuit.Comment: 11 pages including supplementary information, to be published in Nature Physic

Primary thermometry triad at 6 mK in mesoscopic circuits

Quantum physics emerge and develop as temperature is reduced. Although mesoscopic electrical circuits constitute an outstanding platform to explore quantum behavior, the challenge in cooling the electrons impedes their potential. The strong coupling of such micrometer-scale devices with the measurement lines, combined with the weak coupling to the substrate, makes them extremely difficult to thermalize below 10 mK and imposes in-situ thermometers. Here we demonstrate electronic quantum transport at 6 mK in micrometer-scale mesoscopic circuits. The thermometry methods are established by the comparison of three in-situ primary thermometers, each involving a different underlying physics. The employed combination of quantum shot noise, quantum back-action of a resistive circuit and conductance oscillations of a single-electron transistor covers a remarkably broad spectrum of mesoscopic phenomena. The experiment, performed in vacuum using a standard cryogen-free dilution refrigerator, paves the way toward the sub-millikelvin range with additional thermalization and refrigeration techniques.Comment: Article and Supplementar

Children’s mental representations with respect to caregivers and post-traumatic symptomatology in Somatic Symptom Disorders and Disruptive Behavior Disorders

Introduction: In line with literature, the quality of adult-infant interactions and mental representations of the caregivers play an essential role in influencing the children's well-being. Many studies focused the attention on the role of attachment for a better evaluation of child psychopathological outcomes. The flexibility of the child's attachment model gives the opportunity to parents to be helped in modifying their own caregiving quality, encouraging the reflection on the children's state of mind with respect to attachment. The aims of this study were to evaluate: (1) the attachment models in young patients diagnosed with Disruptive Behavior Disorders (DBDs) and Somatic Symptoms Disorders (SSDs); (2) the levels of post-traumatic symptomatology; (3) the association between the attachment models and post-traumatic symptomatology. Methods: Forty Italian patients, aged from 8 to 15, recruited at Gaslini Paediatric Hospital of Genoa, previously diagnosed with SSD (N = 20) and DBD (N = 20) were assessed using the Child Attachment Interview (CAI), the Separation Anxiety Test (SAT), the Trauma Symptom Checklist for Children (TSCC-A). Socio-demographic data were collected. Results: In both the clinical samples, the findings on the distribution of attachment models showed a significant presence of insecure attachment with respect to both parents in more than a half of the patients and high levels of disorganized attachment. No significant differences between DBD and SSD samples were found on post-traumatic symptomatology (Post-Traumatic Stress and Dissociation). Significant differences were found on Depression, Anxiety, and Fantasy subscales. Discussion: This study can provide a detection of dysfunctional aspects in clinical populations. The findings suggest that the quality of the attachment to parents may be a fundamental element to better assess SSD and DBD in children and adolescents. Clinical implications of this study aimed at improving parental caregiving are highlighted

Assessing clinical and psychological features: who are patients showing a nocebo re-action during the drug challenge test?

The nocebo reaction, namely the undesirable effect of an inert substance (placebo), is a phenomenon rarely investigated in literature. A better knowledge of this reaction may help clinicians in the management of these patients in clinical practice. Patients with drug adverse reactions (ADR) undergoing the drug challenge test are an ideal model for studying the nocebo effect, and the study aims to investigate their clinical and psychological features. One hundred and twenty patients (Mage = 46.59, SD = 15.5; 82% female), of which 90 non responders and 30 with nocebo reactions (25%) were recruited, and completed a battery of psychological measures: State-Trait Anxiety Inventory X1-X2, Beck Depression Inventory II, Symptoms Checklist-90-R, Difficulties in Emotion Regulation Scale, Toronto Alexithymia Scale. Clinical features (individual characteristics and ADR clinical history) were collected by clinicians. The results show that older age (p = 0.002), low level of education (p = 0.039) and a depressive tendency (p = 0.030) appear to be potential risk factors for nocebo effects. Although none of the features related to the previous clinical history appear to represent a risk factor for the nocebo reactions (p minor 0.05), significant correlations between some of the clinical and psychological characteristics considered (p values from 0.005 to 0.042) help to better delineate the profile of these reactive patients. A specific training of the sanitary team about psychological aspects is recommendable

Wigner and Kondo physics in quantum point contacts revealed by scanning gate microscopy

Quantum point contacts exhibit mysterious conductance anomalies in addition to well known conductance plateaus at multiples of 2e^2/h. These 0.7 and zero-bias anomalies have been intensively studied, but their microscopic origin in terms of many-body effects is still highly debated. Here we use the charged tip of a scanning gate microscope to tune in situ the electrostatic potential of the point contact. While sweeping the tip distance, we observe repetitive splittings of the zero-bias anomaly, correlated with simultaneous appearances of the 0.7 anomaly. We interpret this behaviour in terms of alternating equilibrium and non-equilibrium Kondo screenings of different spin states localized in the channel. These alternating Kondo effects point towards the presence of a Wigner crystal containing several charges with different parities. Indeed, simulations show that the electron density in the channel is low enough to reach one-dimensional Wigner crystallization over a size controlled by the tip position