QCD at HERA

A review of HERA measurements of structure functions, fragmentation functions and forward jet production is presented.Comment: 12 pages. 13 postscript figures + 1 postscript preprint logo + 1 LaTeX file + 1 style file. Also available at http://ppewww.ph.gla.ac.uk/preprints/98/02/ Invited talk given at SILAFAE9

K→πK \to \pi semileptonic form factors with Nf=2+1+1N_f=2+1+1 Twisted Mass fermions

We present a lattice QCD determination of the vector and scalar form factors of the semileptonic $K \to \pi \ell \nu$ decay which are relevant for the extraction of the CKM matrix element $|V_{us}|$ from experimental data. Our results are based on the gauge configurations produced by the European Twisted Mass Collaboration with $N_f = 2+1+1$ dynamical fermions, which include in the sea, besides two light mass degenerate quarks, also the strange and the charm quarks. We use data simulated at three different values of the lattice spacing and with pion masses as small as $210$ MeV. Our final result for the vector form factor at zero momentum transfer is $f_+(0) = 0.9709 (46)$, where the uncertainty is both statistical and systematic combined in quadrature. Using the latest experimental value of $f_+(0) |V_{us}|$ from $K_{\ell 3}$ decays, we obtain $|V_{us}| = 0.2230 (11)$, which allows to test the unitarity constraint of the Standard Model below the permille level once the determination of $|V_{ud}|$ from superallowed nuclear $\beta$ decays is adopted. A slight tension with unitarity at the level of $\sim 2$ standard deviations is observed. Moreover we present our results for the semileptonic scalar $f_0(q^2)$ and vector $f_+(q^2)$ form factors in the whole range of values of the squared four-momentum transfer $q^2$ measured in $K_{\ell 3}$ decays, obtaining a very good agreement with the momentum dependence of the experimental data. We provide a set of synthetic data points representing our results for the vector and scalar form factors at the physical point for several selected values of $q^2$.Comment: 37 pages, 5 tables, 9 figures; version to appear in PR

Tata Kelola, Konsentrasi Saham Dan Kinerja Perusahaan Agroindustri Indonesia

. This study aims to investigate determinants of firm performance on agro-industrial firms that are listed in the Indonesian Stock Exchange (IDX). Agro-industry sector has contributed 15 percent of Product Domestic Bruto in 2012. Agro-industrial firms has also comparative and competitive advantages compare to other industries. Characteristics of this sectors are renewable resources, labor intensive, and the most resistant in economic crisis in Indonesia in 1998. Modeling of performance is analyzed by performing regression analysis of panel data. This study employs secondary data of 54 companies from year 2010 to 2013. The results show that performance is affected by ownership concentration, the effectiveness of good governance mechanism, especially the function of board of directors (BOD) in conducting their duties, leverage and size of a firm. Except for size variable, all other determinants affects positively on performance, in line with reseach hipothesis. However, board of commissioners, independent commissioners, auditors committee, and dividend payout are not significant factors in enhancing performance. The results can shade some highlights to management, investors and other decision makers to implement better governance practices in agro-industrial firms in Indonesia

Leading isospin-breaking corrections to pion, kaon and charmed-meson masses with Twisted-Mass fermions

We present a lattice computation of the isospin-breaking corrections to pseudoscalar meson masses using the gauge configurations produced by the European Twisted Mass collaboration with $N_f = 2 + 1 + 1$ dynamical quarks at three values of the lattice spacing ($a \simeq 0.062, 0.082$ and $0.089$ fm) with pion masses in the range $M_\pi \simeq 210 - 450$ MeV. The strange and charm quark masses are tuned at their physical values. We adopt the RM123 method based on the combined expansion of the path integral in powers of the $d$- and $u$-quark mass difference ($\widehat{m}_d - \widehat{m}_u$) and of the electromagnetic coupling $\alpha_{em}$. Within the quenched QED approximation, which neglects the effects of the sea-quark charges, and after the extrapolations to the physical pion mass and to the continuum and infinite volume limits, we provide results for the pion, kaon and (for the first time) charmed-meson mass splittings, for the prescription-dependent parameters $\epsilon_{\pi^0}$, \epsilon_\gamma(\overline{MS}, 2~\mbox{GeV}), \epsilon_{K^0}(\overline{MS}, 2~\mbox{GeV}), related to the violations of the Dashen's theorem, and for the light quark mass difference (\widehat{m}_d - \widehat{m}_u)(\overline{MS}, 2~\mbox{GeV}).Comment: 47 pages, 20 figures, 4 tables; comments on QED and QCD splitting prescriptions added; version to appear in PR

\Delta S=2 and \Delta C=2 bag parameters in the SM and beyond from Nf=2+1+1 twisted-mass LQCD

We present unquenched lattice QCD results for the matrix elements of four-fermion operators relevant to the description of the neutral K and D mixing in the Standard Model and its extensions. We have employed simulations with Nf = 2 + 1 + 1 dynamical sea quarks at three values of the lattice spacings in the interval 0.06 - 0.09 fm and pseudoscalar meson masses in the range 210 - 450 MeV. Our results are extrapolated to the continuum limit and to the physical pion mass. Renormalization constants have been determined non-perturbatively in the RI-MOM scheme. In particular, for the Kaon bag-parameter, which is relevant for the \overline{K}^0-K^0 mixing in the Standard Model, we obtain B_K^{RGI} = 0.717(24).Comment: Added comments to error budget discussion; fig.19 corrected. Version to appear in PR

Coupled channel approach to strangeness S = -2 baryon-bayron interactions in Lattice QCD

The baryon-baryon interactions with strangeness S = -2 with the flavor SU(3) breaking are calculated for the first time by using the HAL QCD method extended to coupled channel system in lattice QCD. The potential matrices are extracted from the Nambu-Bethe-Salpeter wave functions obtained by the 2+1 flavor gauge configurations of CP-PACS/JLQCD Collaborations with a physical volume of 1.93 fm cubed and with m_pi/m_K = 0.96, 0.90, 0.86. The spatial structure and the quark mass dependence of the potential matrix in the baryon basis and in the SU(3) basis are investigated.Comment: 17 pages, 15 figure

B fields in OB stars (BOB): FORS2 spectropolarimetric follow-up of the two rare rigidly rotating magnetosphere stars HD23478 and HD345439

Massive B-type stars with strong magnetic fields and fast rotation are very rare and provide a mystery for theories of both star formation and magnetic field evolution. Only two such stars, called sigma Ori E analogs, were previously known. Recently, a team involved in APOGEE, one of the Sloan Digital Sky Survey III programs, announced the discovery of two additional rigidly rotating magnetosphere stars, HD23478 and HD345439. The presence of magnetic fields in these newly discovered sigma Ori E analogs was not investigated in the past. In the framework of our ESO Large Programme, and one normal ESO programme, we carried out low-resolution FORS2 spectropolarimetric observations of HD23478 and HD345439. From the measurements using hydrogen lines, we discover a rather strong longitudinal magnetic field of the order of up to 1.5kG in HD23478, and up to 1.3kG using the entire spectrum. The analysis of HD345439 using four subsequent spectropolarimetric subexposures does not reveal the presence of a magnetic field at a significance level of 3sigma. On the other hand, the inspection of individual subexposures indicates that HD345439 may host a strong magnetic field, rapidly varying over 88 minutes. A hint at the fast rotation of HD345439 is also given by the behaviour of several metallic and He I lines in the low-resolution FORS2 spectra, showing profile variations already on such a short time scale.Comment: 5 pages, 4 figures, 1 table, accepted for publication as a letter to A&