Relativistic description of the charmonium mass spectrum

The charmonium mass spectrum is considered in the framework of the constituent quark model with the relativistic treatment of the c quark. The obtained masses are in good agreement with the existing experimental data including the mass of eta_c(2S).Comment: 5 page

Simple quantum cosmology: Vacuum energy and initial state

A static non-singular 10-dimensional closed Friedmann universe of Planck size, filled with a perfect fluid with an equation of state with w = -2/3, can arise spontaneously by a quantum fluctuation from nothing in 11-dimensional spacetime. A quantum transition from this state can initiate the inflationary quantum cosmology outlined in Ref. 2 [General Relativity and Gravitation 33, 1415, 2001 - gr-qc/0103021]. With no fine-tuning, that cosmology predicts about 60 e-folds of inflation and a vacuum energy density depending only on the number of extra space dimensions (seven), G, h, c and the ratio between the strength of gravity and the strength of the strong force. The fraction of the total energy in the universe represented by this vacuum energy depends on the Hubble constant. Hubble constant estimates from WMAP, SDSS, the Hubble Key Project and Sunyaev-Zeldovich and X-ray flux measurements range from 60 to 72 km/(Mpc sec). With a mid-range Hubble constant of 65 km/(Mpc sec), the model in Ref. 2 predicts Omega-sub-Lambda = 0.7Comment: To be published in General Relativity and Gravitation, Vol. 37, May 2005. 5 pages, no figure

The Nuclear Reactions in Standard BBN

Nowadays, the Cosmic Microwave Background (CMB) anisotropies studies accurately determine the baryon fraction omega_b, showing an overall and striking agreement with previous determinations of omega_b obtained from Big Bang Nucleosynthesis (BBN). However, a deeper comparison of BBN predictions with the determinations of the primordial light nuclides abundances shows slight tensions, motivating an effort to further improve the accuracy of theoretical predictions, as well as to better evaluate systematics in both observations and nuclear reactions measurements. We present some results of an important step towards an increasing precision of BBN predictions, namely an updated and critical review of the nuclear network, and a new protocol to perform the nuclear data regression.Comment: 4 pp.,4figs. Few typos corrected and updated refs. to match the version appearing in the proceedings of Conference ``Nuclei in the Cosmos VIII'', Vancouver, BC, Canada, 19-23 Jul 2004, published in Nucl. Phys.

Ultracentrifugation for ultrafine nanodiamond fractionation

In this paper we propose a method for ultrafine fractionation of nanodiamonds using the differential centrifugation in the fields up to 215000g. The developed protocols yield 4-6 nm fraction giving main contribution to the light scattering intensity. The desired 4-6 nm fraction can be obtained from various types of initial nanodiamonds: three types of detonation nanodiamonds differing in purifying methods, laser synthesis nanodiamonds and nanodiamonds made by milling. The characterization of the obtained hydrosols was conducted with Dynamic Light Scattering, Zeta potential measurements, powder XRD and TEM. According to powder XRD and TEM data ultracentrifugation also leads to a further fractionation of the primary diamond nanocrystallites in the hydrosols from 4 to 2 nm.Comment: 7 pages, 8 figure

The running of the electromagnetic coupling alpha in small-angle Bhabha scattering

A method to determine the running of alpha from a measurement of small-angle Bhabha scattering is proposed and worked out. The method is suited to high statistics experiments at e+e- colliders, which are equipped with luminometers in the appropriate angular region. A new simulation code predicting small-angle Bhabha scattering is also presentedComment: 15 pages, 3 Postscript figure

A Scintillating Fiber Hodoscope for a Bremstrahlung Luminosity Monitor at an Electron−-Positron Collider

The performance of a scintillating fiber (2mm diameter) position sensitive detector ($4.8 \times 4.8$ cm$^2$ active area) for the single bremstrahlung luminosity monitor at the VEPP-2M electron-positron collider in Novosibirsk, Russia is described. Custom electronics is triggered by coincident hits in the X and Y planes of 24 fibers each, and reduces 64 PMT signals to a 10 bit (X,Y) address. Hits are accumulated (10 kHz) in memory and display (few Hz) the VEPP-2M collision vertex. Fitting the strongly peaked distribution ( $\sim$ 3-4 mm at 1.6m from the collision vertex of VEPP-2M ) to the expected QED angular distribution yields a background in agreement with an independent determination of the VEPP-2M luminosity.Comment: LaTeX with REVTeX style and options: multicol,aps. 8 pages, postscript figures separate from text. Accepted in Review of Scientific Instruments (~ Aug 1996