Volume element structure and roton-maxon-phonon excitations in superfluid helium beyond the Gross-Pitaevskii approximation

We propose a theory which deals with the structure and interactions of volume elements in liquid helium II. The approach consists of two nested models linked via parametric space. The short-wavelength part describes the interior structure of the fluid element using a non-perturbative approach based on the logarithmic wave equation; it suggests the Gaussian-like behaviour of the element's interior density and interparticle interaction potential. The long-wavelength part is the quantum many-body theory of such elements which deals with their dynamics and interactions. Our approach leads to a unified description of the phonon, maxon and roton excitations, and has noteworthy agreement with experiment: with one essential parameter to fit we reproduce at high accuracy not only the roton minimum but also the neighboring local maximum as well as the sound velocity and structure factor.Comment: 9 pages, 6 figure

Measurement of the photon+b+b-jet production differential cross section in ppˉp\bar{p} collisions at \sqrt{s}=1.96~\TeV

We present measurements of the differential cross section dsigma/dpT_gamma for the inclusive production of a photon in association with a b-quark jet for photons with rapidities |y_gamma|< 1.0 and 30<pT_gamma <300 GeV, as well as for photons with 1.5<|y_gamma|< 2.5 and 30< pT_gamma <200 GeV, where pT_gamma is the photon transverse momentum. The b-quark jets are required to have pT>15 GeV and rapidity |y_jet| < 1.5. The results are based on data corresponding to an integrated luminosity of 8.7 fb^-1, recorded with the D0 detector at the Fermilab Tevatron $p\bar{p}$ Collider at sqrt(s)=1.96 TeV. The measured cross sections are compared with next-to-leading order perturbative QCD calculations using different sets of parton distribution functions as well as to predictions based on the kT-factorization QCD approach, and those from the Sherpa and Pythia Monte Carlo event generators.Comment: 10 pages, 9 figures, submitted to Phys. Lett.

Search for pair production of the scalar top quark in muon+tau final states

We present a search for the pair production of scalar top quarks ($\tilde{t}_{1}$), the lightest supersymmetric partners of the top quarks, in $p\bar{p}$ collisions at a center-of-mass energy of 1.96 TeV, using data corresponding to an integrated luminosity of {7.3 $fb^{-1}$} collected with the \dzero experiment at the Fermilab Tevatron Collider. Each scalar top quark is assumed to decay into a $b$ quark, a charged lepton, and a scalar neutrino ($\tilde{\nu}$). We investigate final states arising from $\tilde{t}_{1} \bar{\tilde{t}_{1}} \rightarrow b\bar{b}\mu\tau \tilde{\nu} \tilde{\nu}$ and $\tilde{t}_{1} \bar{\tilde{t}_{1}} \rightarrow b\bar{b}\tau\tau \tilde{\nu} \tilde{\nu}$. With no significant excess of events observed above the background expected from the standard model, we set exclusion limits on this production process in the ($m_{\tilde{t}_{1}}$,$m_{\tilde{\nu}}$) plane.Comment: Submitted to Phys. Lett.

Pilot study on university students' opinion about STEM studies at higher education

The percentages of women enrolled in higher education in the STEM sector are significantly lower than those of men. Overall, gender representation in science, technology, engineering and mathematics degrees in Europe is not balanced. The Leaky Pipeline phenomenon, marked by gender stereotypes, makes the latent gender gap a relevant topic of study. Studies exist on academic performance, self-perception, self-efficacy, outcome expectations; however, studying gender stereotypes linked to STEM studies is also essential. It is necessary to know the social and family context in which young people have grown up, as well as their perception of such studies. To study gender stereotypes of university students about STEM studies, a questionnaire has been designed for empirical validation. For the design of the instrument, to be validated, items from other instruments have been taken and adapted to Spanish. After the design of the instrument, an online pilot study has been applied in the University of Salamanca, the University of Valencia and the Polytechnic University of Valencia. A total of 115 people answered the questionnaire. The results of the pilot study reveal that the study sample is not particularly marked by gender stereotypes about gender equality in STEM. Also, the sample is receptive to learning about science and applying it in their lives. On the other hand, the idea that women have to give up their studies and careers to look after their families and children is rejected. The idea that men are more interested in university studies than women is also rejected. At the same time, the sample is aware of the difficulties that women encounter in the STEM sector. Another optimistic point of the results is that there are no alarming data on bad experiences due to gender. In the future, the study will be replicated on a larger scale