Evidence for the Strong Effect of Gas Removal on the Internal Dynamics of Young Stellar Clusters

We present detailed luminosity profiles of the young massive clusters M82-F, NGC 1569-A, and NGC 1705-1 which show significant departures from equilibrium (King and EFF) profiles. We compare these profiles with those from N-body simulations of clusters which have undergone the rapid removal of a significant fraction of their mass due to gas expulsion. We show that the observations and simulations agree very well with each other suggesting that these young clusters are undergoing violent relaxation and are also losing a significant fraction of their stellar mass. That these clusters are not in equilibrium can explain the discrepant mass-to-light ratios observed in many young clusters with respect to simple stellar population models without resorting to non-standard initial stellar mass functions as claimed for M82-F and NGC 1705-1. We also discuss the effect of rapid gas removal on the complete disruption of a large fraction of young massive clusters (``infant mortality''). Finally we note that even bound clusters may lose >50% of their initial stellar mass due to rapid gas loss (``infant weight-loss'').Comment: 6 pages, 3 figures, MNRAS letters, accepte

Dispersive analysis of omega --> 3pi and phi --> 3pi decays

We study the three-pion decays of the lightest isoscalar vector mesons, omega and phi, in a dispersive framework that allows for a consistent description of final-state interactions between all three pions. Our results are solely dependent on the phenomenological input for the pion-pion P-wave scattering phase shift. We predict the Dalitz plot distributions for both decays and compare our findings to recent measurements of the phi --> 3pi Dalitz plot by the KLOE and CMD-2 collaborations. Dalitz plot parameters for future precision measurements of omega --> 3pi are predicted. We also calculate the pi-pi P-wave inelasticity contribution from omega-pi intermediate states.Comment: 23 pages, 18 figures; discussion extended, Appendix D added, matches version published in EPJ

Dispersion relations for η′→ηππ\eta'\to\eta\pi\pi

We present a dispersive analysis of the decay amplitude for $\eta'\to\eta\pi\pi$ that is based on the fundamental principles of analyticity and unitarity. In this framework, final-state interactions are fully taken into account. Our dispersive representation relies only on input for the $\pi\pi$ and $\pi\eta$ scattering phase shifts. Isospin symmetry allows us to describe both the charged and neutral decay channel in terms of the same function. The dispersion relation contains subtraction constants that cannot be fixed by unitarity. We determine these parameters by a fit to Dalitz-plot data from the VES and BES-III experiments. We study the prediction of a low-energy theorem and compare the dispersive fit to variants of chiral perturbation theory.Comment: 22 pages, 10 figures; v2: added footnote, version published in EPJ

PENGARUH PENGGUNAAN CUTTING FLUID DAN PEMILIHAN FEED RATE TERHADAP KEKASARAN PERMUKAAN DAN KEPRESISIAN MATERIAL ALUMINIUM MENGGUNAKAN MESIN MILLING CNC

Ada banyak faktor yang mempengaruhi kualitas produk yang dihasilkan dari proses milling. Kualitas produk kebanyakan tentang kekasaran permukaan dan kepresisian. Faktor-faktor yang mempengaruhi adalah pemilihan parameter pemotongan dan penggunaan cutting fluid. Penelitian ini dilakukan untuk mengetahui pengaruh penggunaan cutting fluid dan pemilihan feed rate terhadap kekasaran permukaan dan kepresisian material aluminium menggunakan mesin milling CNC. Pada penelitian ini menggunakan mesin milling CNC Mitsubishi M70. Variabel bebas feed rate 20, 32, 45, 69, 108 mm/min. Tiap variasi feed rate diberi perlakuan menggunakan cutting fluid dan tanpa menggunakan cutting fluid. Cutting fluid yang digunakan yaitu oli bromus yang dicampur dengan air. Pengujian yang dilakukan adalah uji kakasaran permukaan, dan uji kepresisian. Hasil penelitian ini menunjukkan bahwa semakin tinggi feed rate maka kekasaran permukaan semakin tinggi (berbanding lurus). Penggunaan cutting fluid berpengaruh terhadap kekasaran permukaan. Nilai kekasaran pada variasi feed rate 20, 32, 45, 69, 108 mm/min menggunakan cutting fluid, menunjukkan nilai kekasaran berturut-turut sebesar 0,442; 0,484; 0,553; 0,643; 0,797 µm. Nilai kekasaran permukaan tanpa menggunakan menggunakan cutting fluid menunjukkan nilai kekasaran 0,470; 0,517; 0,582; 0;662; 0,847 µm. Berdasarkan hasil analisis statistik menggunakan two way ANOVA, disimpulkan bahwa penggunaan cutting fluid dan variasi feed rate berpengaruh terhadap kepresisian dengan tingkat keyakinan 95 %. Pada pengukuran dimensi A variasi feed rate 20, 32, 45,69,108 mm/min menggunakan cutting fluid, tingkat kepresisiannya sebesar 99,999348; 99,99929; 99,999304; 99,999261; 99,9992 %. Pada variasi tanpa menggunakan cutting fluid, tingkat kepresisiannya sebesar 99,999188; 99,999184; 99,999037; 99;998884; 99,998684 %

Dispersive analysis of the pion transition form factor

We analyze the pion transition form factor using dispersion theory. We calculate the singly-virtual form factor in the time-like region based on data for the $e^+e^-\to 3\pi$ cross section, generalizing previous studies on $\omega,\phi\to3\pi$ decays and $\gamma\pi\to\pi\pi$ scattering, and verify our result by comparing to $e^+e^-\to\pi^0\gamma$ data. We perform the analytic continuation to the space-like region, predicting the poorly-constrained space-like transition form factor below 1 GeV, and extract the slope of the form factor at vanishing momentum transfer $a_\pi=(30.7\pm0.6)\times 10^{-3}$. We derive the dispersive formalism necessary for the extension of these results to the doubly-virtual case, as required for the pion-pole contribution to hadronic light-by-light scattering in the anomalous magnetic moment of the muon.Comment: 13 pages, 5 figures, journal versio

Thermophysical properties of warm dense hydrogen

We study the thermophysical properties of warm dense hydrogen using quantum molecular dynamics simulations. New results are presented for the pair distribution functions, the equation of state, the Hugoniot curve, and the reflectivity. We compare with available experimental data and predictions of the chemical picture. Especially, we discuss the nonmetal-to-metal transition which occurs at about 40 GPa in the dense fluid