arXiv subjects

N. Poljak

Publications and source records attributed to N. Poljak.

4 recordsLinked to original sources

arXiv2019

Studies of the delayed discharge propagation in the Gas Electron Multiplier (GEM)

This paper presents an investigation of the discharge propagation (DP) to the readout electrode that occurs with a microsecond time delay after a primary discharge that develops inside a GEM foil hole. A single hole THGEM (THick GEM) foil that enables a controlled discharge position and the induction of primary discharge with an over-voltage in the THGEM foil has been used in the initial DP measurements. In order to justify the use of a custom-made THGEM foil, additional measurements were made with a standard GEM foil. Correlated optical (with an ordinary SLR and a high-speed camera) and electrical measurements of the delayed DP were made for Ne-CO$_2$-N$_2$ (90-10-5) mixture and with different powering configurations. Measurements show that the delayed DP happens without a drift field, with an inverted induction field, inverted THGEM voltages or an inverted drift field. After the primary discharge, there is a charge transfer in the induction region at an induction field value below that of the onset field for DP. In the time between the primary discharge and the delayed DP, three different current regimes are observed, which suggests multiple charge transfer mechanisms in the induction region. High-speed camera recordings provide valuable insight into the time evolution of the primary and the delayed DP, especially when correlated with electrical measurements.

physics.ins-det↗

arXiv2018

Physionary - a scientific version of Pictionary

We describe a variant of the popular game "Pictionary" based on terms used in elementary and high school physics. We believe that drawing of physical terms helps students develop a deeper understanding of physical concepts behind them, as well as apply them in everyday situations.

physics.ed-ph↗

arXiv2011

STAR results and perspectives on transverse spin asymmetries

The STAR collaboration reported precision measurements on the transverse single spin asymmetries for the production of forward $π^0$ mesons from polarized proton collisions at $\sqrt{s}=$ 200 GeV. To disentangle contributions to measured forward asymmetries one has to look beyond inclusive $π^0$ production to the production of forward jets or direct photons. In 2006, STAR with the Forward Pion Detector++ (FPD++) in place, collected 6.8 pb$^{-1}$ of forward data with an average polarization of 60%. FPD++ had sufficient acceptance for "jet-like" objects, which are clustered responses of an electromagnetic calorimeter primarily sensitive to incident photons, electrons and positrons. For these objects, the angle of the outgoing leading $π^0$ with respect to the fragmenting parton was reconstructed, thus enabling us to disentangle the contributions to the forward $π^0$ asymmetries. The simulated data set shows that on average there are approximately 2.5 fragmenting mesons per one "jet-like" object, making them reasonably "jetty". Preliminary results provide no evidence of measured contributions to the asymmetry from jet fragmentation, implying the Sivers distribution functions play a substantial role in producing the large inclusive forward $π^0$ asymmetries. A similar effort was made in the mid-rapidity $(|η|<1)$ region of the STAR detector, where 2.2 pb$^{-1}$ of data was collected. We present progress made by making measurements of the azimuthal asymmetry of leading charged pions in jets produced by transversely polarized proton collisions.

hep-ex↗

arXiv2011

Forward Jet-like Event Spin-dependent Properties in Polarized p+p Collisions at $\sqrt{s}=200$ GeV

The STAR collaboration has reported precision measurements on the transverse single spin asymmetries for the production of forward $π^0$ mesons from polarized proton collisions at the center of mass energy of 200 GeV. Disentangling contributions to forward asymmetries requires one to look beyond inclusive neutral pion production to the production of forward jets or direct photons. During the RHIC running in the year 2006, STAR with the Forward Pion Detector++ (FPD++) in place collected 6.8 inverse picobarn of data with an average polarization of 60%. FPD++ had sufficient acceptance for "jetlike" objects, which are clustered responses of an electromagnetic calorimeter primarily sensitive to incident photons, electrons and positrons. For the "jet-like" objects, we reconstructed the angle of the outgoing leading neutral pion with respect to the fragmenting parton, thus enabling us to disentangle the contributions to the forward $π^0$ asymmetries. The simulated data set shows that on average there are approximately 2.5 fragmenting mesons per one "jet-like" object. Preliminary FPD++ results provide no evidence of measured contributions to the asymmetry from jet fragmentation, implying the Sivers distribution functions play a substantial role in producing the large inclusive $π^0$ asymmetries previously measured by STAR.

hep-ex↗