An Inconsistency in the Simulation of Bose-Einstein Correlations

We show that the formalism commonly used to implement Bose-Einstein correlations in Monte-Carlo simulations can lead to values of the two-particle correlator significantly smaller than unity, in the case of sources with strong position-momentum correlations. This is more pronounced when the phase space of the emitted particles is strongly reduced by experimental acceptance or kinematic analysis selections. It is inconsistent with general principles according to which the Bose-Einstein correlator is larger than unity. This inconsistency seems to be rooted in the fact that quantum mechanical localization properties are not taken into account properly.Comment: 10 pages, LaTe

Virtual Reality 3rd person camera behavior modes

We describe and evaluate five different level design independent modes of handling camera behavior in the 3rd person game LizzE – And the Light of Dreams in Virtual Reality. The behavior of the different modes will each be illustrated in detail. To evaluate the modes A: Fast circling, B: Lazy Circling, C: No Circling, D: Blink circling and E: Buffered pulling, an experimental study with 33 subjects was conducted. An analysis of the resulting data will show why Buffered pulling seems to be the most promising of the examined modes. We elaborate on the quantitative and qualitative hybrid experiment design and methodology. Eventually the advantages and disadvantages of the five tested modes are discussed in terms of supporting the gameplay, player enjoyment, in game performance and the tendency to induce nausea

An experiment design: investigating VR locomotion & virtual object interaction mechanics

In this paper, we describe an experiment outline on investigating design and user experience related aspects of several virtual reality locomotion and virtual object interaction mechanics. These mechanics will be based on consumer hardware like a common game controllers, an infrared hand and finger tracking device, VR hand controllers and an omnidirectional treadmill. Corresponding related work will contextualize and motivate this research. The projected experimental study will be based on user test sessions with a specifically developed 1st person VR puzzle horror game, called Gooze. A hybrid approach of self-assessment, in-game parameter tracking and session observations will be proposed for the investigation. Statistical analysis methods will be suggested to evaluate results. Furthermore, this paper will give an overview of the game and elaborate on design, gameplay and user experience related insights of already conducted informal pre-studies with it

Local multiplayer immersion affected by 3D stereoscopy

In this paper, we describe an experimental study, which evaluates how 3D stereoscopy affects player immersion in a possibly very distracting local multiplayer game. The game “Nicely Dicely” was specifically developed for this purpose, with 3D stereoscopy in mind, right from the beginning. Groups of participants were competitively playing the game in non-3D monoscopic and 3D stereoscopic presentations via a 3D compatible projector and corresponding active shutter glasses. In the following, we elaborate on the game and our quantitative and qualitative hybrid experiment design and methodology. An analysis of the resulting data will show that, indeed 3D stereoscopy significantly increases spatial presence, involvement and player immersion, even in a local multiplayer situation. Furthermore, some guiding insights relating the game’s design will be illustrated

UX evaluation of VR locomotion & virtual object interaction mechanics

Virtual Reality (VR) Interactions like in Ready Player One? Locomotion (LOC) and Virtual Object Interaction (VOI) are two key areas of concern, when designing and developing VR games and other VR applications. This paper describes a study of three interaction modes and their underlying VOI and LOC mechanics, using a range of consumer-oriented VR input setups, spanning from gamepad, over Spatially Tracked Hand Controllers, to Controllerless Hand Tracking and Omnidirectional Treadmill. All corresponding mechanics were implemented in the specifically developed, optimized and polished “real-world” game Gooze, to test them in a real-world scenario with corresponding challenges in gaming and human computer interaction. A within-subjects experiment with 89 participants using qualitative and quantitative analysis methods was conducted. The interaction modes and their mechanics were evaluated based on the four User Experience aspects: Player Enjoyment, Support of Gameplay, Simulator Sickness and Presence, with the latter being subdivided into the four sub-parameters: General Presence, Spatial Presence, Involvement and Experienced Realism, according to the igroup Presence Questionnaire. The paper concludes with summarizing the individual advantages and disadvantages of the assessed interaction modes

“VRification”: applying virtual reality to digital games

In the following, we discuss the process of applying virtual reality to digital games. We named this process “VRification” and will elaborate on some of its opportunities and issues. Based on a literature survey and professional practice, this work covers several examples of VR games, which were intended as such from the beginning (Job Simulator and Lucky’s Tale) and others, which were ported to VR after their initial release (DOOM VR and LizzE). We conclude that, for VR games, it is essential to be optimized for the full potential of targeted interface technologies. Furthermore, porting former-non-VR games to VR can create successful user experiences, when aiming for the same high standard of optimization, especially regarding simulator sickness

Non-Abelian Energy Loss at Finite Opacity

A systematic expansion in opacity, $L/\lambda$, is used to clarify the non-linear behavior of induced gluon radiation in quark-gluon plasmas. The inclusive differential gluon distribution is calculated up to second order in opacity and compared to the zeroth order (factorization) limit. The opacity expansion makes it possible to take finite kinematic constraints into account that suppress jet quenching in nuclear collisions below RHIC ($\sqrt{s}=200$ AGeV) energies.Comment: 4 pages (revtex) with 3 eps figures, submitted to PR

Jet multiplicities as the QGP thermometer

It is proposed to use the energy behavior of mean multiplicities of jets propagating in a nuclear medium as the thermometer of this medium during the collision phases. The qualitative effects are demonstrated in the framework of the fixed coupling QCD with account of jet quenching.Comment: Modify version of hep-ph/0509344, 3 figure

Low-pT Collective Flow Induces High-pT Jet Quenching

Data on low-pT hadronic spectra are widely regarded as evidence of a hydrodynamic expansion in nucleus-nucleus collisions. In this interpretation, different hadron species emerge from a common medium that has built up a strong collective velocity field. Here, we show that the existence of a collective flow field implies characteristic modifications of high-pT parton fragmentation. We generalize the formalism of parton energy loss to the case of flow-induced, oriented momentum transfer. We also discuss how to embed this calculation in hydrodynamic simulations. Flow effects are found to result generically in characteristic asymmetries in the eta-phi-plane of jet energy distributions and of multiplicity distributions associated to high-pT trigger particles. But collective flow also contributes to the medium-induced suppression of single inclusive high-pT hadron spectra. In particular, we find that low-pT elliptic flow can induce a sizeable additional contribution to the high-pT azimuthal asymmetry by selective elimination of those hard partons which propagate with significant inclination against the flow field. This reduces at least partially the recently observed problem that models of parton energy loss tend to underpredict the large azimuthal asymmetry v2 of high-pT hadronic spectra in semi-peripheral Au+Au collisions.Comment: 26 pages LaTeX, 11 eps-figure

Identified Hadrons and Jet Chemistry for p+p and Au+Au Collisions at RHIC

The study of hadron spectra at high $p_{T}$ in p+p collisions provides a good test of perturbative quantum chromo-dynamic calculations (pQCD) and baseline for measurements of nuclear modification factors in Au+Au collisions. Using events triggered by the Barrel Electro-Magnetic Calorimeter, identified charged hadron transverse momentum ($p_T$) spectra are measured up to 15 GeV/$c$ at mid-rapidity ($\mid y\mid$ $<$ 0.5) and neutral kaon $p_T$ spectra up to 12 GeV/$c$ in p + p collisions at $\sqrt{s_{NN}}$ = 200 GeV. The particle ratios of $p/\pi^{+}$, $\bar{p}/\pi^{-}$ and $K^{\pm,0}$ / $\pi^{\pm}$ in p + p collisions are shown and compared with next-to-leading order pQCD calculations. In central Au+Au collisions, we report nuclear modification factors ($R_{AA}$) for pion, kaon, proton and $\rho$ and discuss several model calculations: color-charge dependence of jet quenching and jet conversion. Finally, centrality dependence of $R_{AA}$ at high $p_T$ ($>$ 5.5 GeV/c) for kaon are compared with that of pion in Au + Au collisions at 200 GeV.Comment: 6 pages, 4 figures, SQM 2009 contributio