Nanostructured target fabrication with metal and semiconductor nanoparticles

The development of ultra-intense high-energy (≫1 J) short (<1 ps) laser pulses in the last decade hasenabled the acceleration of high-energy short-pulse proton beams. A key parameter for enhancing theacceleration regime is the laser-to-target absorption, which heavily depends on the target structureand material. In this work, we present the realization of a nanostructured target with a sub-laserwavelength nano-layer in the front surface as a possible candidate for improving the absorption. Thenanostructuredfilm was realized by a simpler and cheaper method than using conventionallithographic techniques: A colloidal solution of metallic or semiconductor nanoparticles (NPs) wasproduced by laser ablation and, after a heating and sonication process, was spray-dried on the frontsurface of an aluminum target. The obtained nanostructuredfilm with a thickness of 1μm appears, atmorphological and chemical analysis, uniformly nanostructured and distributed on the target surfacewithout the presence of oxides or external contaminants. Finally, the size of the NPs can be tuned fromtens to hundreds of nanometers simply by varying the growth parameters (i.e., irradiation time,fluence, and laser beam energy

Laser-Plasma driven synthesis of carbon-based nanomaterials

In this paper we introduce a laser-plasma driven method for the production of carbon based nanomaterials and in particular bi- and few-layers of Graphene. This is obtained by using laser-plasma exfoliation of amorphous Graphite in a liquid solution, employing a laser with energy in the order of 0.5 J/mm2. Raman and XPS analysis of a carbon colloidal performed at different irradiation stages indicate the formation of Graphene multilayers with an increasing number of layers: the amount of layers varies from a monolayer obtained in the first few seconds of the laser irradiation, up to two layers obtained after 10 s, and finally to Graphite and amorphous carbon obtained after 40 s of irradiation. The obtained colloidals are pure, without any presence of impurities or Graphene oxides, and can easily be deposited onto large surfaces (in the order of cm2) for being characterized or for being used in diverse applications

Inelastic Dark Matter and the SABRE Experiment

We present here the sensitivity of the SABRE (Sodium iodide with Active Background REjection) experiment to benchmark proto-philic, spin dependent, Inelastic Dark Matter models previously proposed due to their lowered tension with existing experimental results. We perform fits to cross section, mass, and mass splitting values to find the best fit to DAMA/LIBRA data for these models. In this analysis, we consider the Standard Halo Model (SHM), as well as an interesting extension upon it, the SHM+Stream distribution, to investigate the influence of the Dark Matter velocity distribution upon experimental sensitivity and whether or not its consideration may be able to help relieve the present experimental tension. Based on our analysis, SABRE should be sensitive to all the three benchmark models within 3-5 years of data taking.Comment: Adjusted for full DAMA run 1+2 efficiency. Updated to match published versio

In situ study of nucleation and aggregation phases for nanoparticles grown by laser-driven methods

In the last decades, nanomaterials and nanotechnologies have become fundamental and irreplaceable in many fields of science and technology. When used in applications, their properties depend on many factors such as size, shape, internal structure and composition. For this, exact knowledge of their structural features is essential when developing fabrication technologies and searching for new types of nanostructures or nanoparticles with specific properties. For the latter, the knowledge of the precise temporal evolution of the growth processes is fundamental when it comes to industrial production and applications. Here we present a method to control, with very high precision, the starting of the aggregation phase during the Laser Ablation in solution growth process. This is obtained by monitoring the optical absorption of the colloidal solution. We apply this control method on the most popular metallic nanoparticle materials (Ag, Al, Co, and Ti) and verify the technique using morphological analysis conducted by AFM and SEM microscopy. The experimental results are explained in terms of Mie extinction theory and Thermal Model for Laser Ablatio

Laser-Accelerated proton beams as diagnostics for cultural heritage

This paper introduces the first use of laser-generated proton beams as diagnostic for materials of interest in the domain of Cultural Heritage. Using laser-accelerated protons, as generated by interaction of a high-power short-pulse laser with a solid target, we can produce proton-induced X-ray emission spectroscopies (PIXE). By correctly tuning the proton flux on the sample, we are able to perform the PIXE in a single shot without provoking more damage to the sample than conventional methodologies. We verify this by experimentally irradiating materials of interest in the Cultural Heritage with laser-accelerated protons and measuring the PIXE emission. The morphological and chemical analysis of the sample before and after irradiation are compared in order to assess the damage provoked to the artifact. Montecarlo simulations confirm that the temperature in the sample stays safely below the melting point. Compared to conventional diagnostic methodologies, laser-driven PIXE has the advantage of being potentially quicker and more efficien

CP asymmetries at D0

Using two independent measurements of the semileptonic CP asymmetry in the $B_s$ system, we constrain the CP violating phase of the $B_s$ system to be $\phi_s = -0.70^{+0.47}_{-0.39}$. The data sample corresponds to an integrated luminosity of 1.1 fb$^{-1}$ accumulated with D0 detector at the Fermilab Tevatron collider. We also measure the direct CP violating asymmetry in the decay $B^+ \to J/\psi K^+$ to be $A_{CP}(B^+ \to J/\psi K^+) = +0.0067 \pm 0.0074$(stat)$\pm0.0026$(syst). The data corresponds to an integrated luminosity of 1.6 fb$^{-1}$.Comment: contributed paper to EPS07, Manchester, UK, manuscript number EPSHEPP17

Analysis of B→a1(1260)(b1(1235))K∗B \to a_1(1260)(b_1(1235))K^* decays in the perturbative QCD approach

Within the framework of perturbative QCD approach, we study the charmless two-body decays $B\to a_1(1260)K^*, b_1(1235)K^*$. Using the decays constants and the light-cone distribution amplitudes for these mesons derived from the QCD sum rule method, we find the following results: (a) Our predictions for the branching ratios are consistent well with the QCDF results within errors, but much larger than the naive factorization approach calculation values. (b) We predict that the anomalous polarizations occurring in the decays $B\to \phi K^*, \rho K^*$ also happen in the decays $B\to a_1K^*$, while do not happen in the decays $B\to b_1K^*$. Here the contributions from the annihilation diagrams play an important role to explain the lager transverse polarizations in the decays $B\to a_1K^*$, while they are not sensitive to the polarizations in decays $B\to b_1K^*$. (c) Our predictions for the direct CP-asymmetries agree well with the QCDF results within errors. The decays $\bar B^0\to b^{+}_1K^{*-}, B^-\to b^{0}_1K^{*-}$ have larger direct CP-asymmetries, which could be measured by the present LHCb experiments.Comment: 12pages, 1figures. arXiv admin note: substantial text overlap with arXiv:1203.5913, arXiv:1203.591

QCD Approach to B->D \pi Decays and CP Violation

The branching ratios and CP violations of the $B\to D\pi$ decays, including both the color-allowed and the color-suppressed modes, are investigated in detail within QCD framework by considering all diagrams which lead to three effective currents of two quarks. An intrinsic mass scale as a dynamical gluon mass is introduced to treat the infrared divergence caused by the soft collinear approximation in the endpoint regions, and the Cutkosky rule is adopted to deal with a physical-region singularity of the on mass-shell quark propagators. When the dynamical gluon mass $\mu_g$ is regarded as a universal scale, it is extracted to be around $\mu_g = 440$ MeV from one of the well-measured $B\to D\pi$ decay modes. The resulting predictions for all branching ratios are in agreement with the current experimental measurements. As these decays have no penguin contributions, there are no direct $CP$ asymmetries. Due to interference between the Cabibbo-suppressed and the Cabibbo-favored amplitudes, mixing-induced CP violations are predicted in the $B\to D^{\pm}\pi^{\mp}$ decays to be consistent with the experimental data at 1-$\sigma$ level. More precise measurements will be helpful to extract weak angle $2\beta+\gamma$.Comment: 21pages,5 figures,3 tables, typos corrected and numerical result for one of decay channels is improve