A Dual-Species Atom Interferometer Payload for Operation on Sounding Rockets

We report on the design and the construction of a sounding rocket payload capable of performing atom interferometry with Bose-Einstein condensates of 41 K and 87 Rb. The apparatus is designed to be launched in two consecutive missions with a VSB-30 sounding rocket and is qualified to withstand the expected vibrational loads of 1.8 g root-mean-square in a frequency range between 20–2000 Hz and the expected static loads during ascent and re-entry of 25 g. We present a modular design of the scientific payload comprising a physics package, a laser system, an electronics system and a battery module. A dedicated on-board software provides a largely automated process of predefined experiments. To operate the payload safely in laboratory and flight mode, a thermal control system and ground support equipment has been implemented and will be presented. The payload presented here represents a cornerstone for future applications of matter wave interferometry with ultracold atoms on satellites

Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions

We present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Forward-central two-particle correlations in p-Pb collisions at root s(NN)=5.02 TeV

Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 2GeV/c. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B. V.Peer reviewe

Event-shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at root(NN)-N-S=2.76 TeV

Peer reviewe

Elliptic flow of muons from heavy-flavour hadron decays at forward rapidity in Pb-Pb collisions at root s(NN)=2.76TeV

The elliptic flow, v(2), of muons from heavy-flavour hadron decays at forward rapidity (2.5 <y <4) is measured in Pb-Pb collisions at root s(NN)= 2.76TeVwith the ALICE detector at the LHC. The scalar product, two- and four-particle Q cumulants and Lee-Yang zeros methods are used. The dependence of the v(2) of muons from heavy-flavour hadron decays on the collision centrality, in the range 0-40%, and on transverse momentum, p(T), is studied in the interval 3 <p(T)<10 GeV/c. A positive v(2) is observed with the scalar product and two-particle Q cumulants in semi-central collisions (10-20% and 20-40% centrality classes) for the p(T) interval from 3 to about 5GeV/c with a significance larger than 3 sigma, based on the combination of statistical and systematic uncertainties. The v(2) magnitude tends to decrease towards more central collisions and with increasing pT. It becomes compatible with zero in the interval 6 <p(T)<10 GeV/c. The results are compared to models describing the interaction of heavy quarks and open heavy-flavour hadrons with the high-density medium formed in high-energy heavy-ion collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V.Peer reviewe

Pseudorapidity and transverse-momentum distributions of charged particles in proton-proton collisions at root s=13 TeV

The pseudorapidity (eta) and transverse-momentum (p(T)) distributions of charged particles produced in proton-proton collisions are measured at the centre-of-mass energy root s = 13 TeV. The pseudorapidity distribution in vertical bar eta vertical bar <1.8 is reported for inelastic events and for events with at least one charged particle in vertical bar eta vertical bar <1. The pseudorapidity density of charged particles produced in the pseudorapidity region vertical bar eta vertical bar <0.5 is 5.31 +/- 0.18 and 6.46 +/- 0.19 for the two event classes, respectively. The transverse-momentum distribution of charged particles is measured in the range 0.15 <p(T) <20 GeV/c and vertical bar eta vertical bar <0.8 for events with at least one charged particle in vertical bar eta vertical bar <1. The evolution of the transverse momentum spectra of charged particles is also investigated as a function of event multiplicity. The results are compared with calculations from PYTHIA and EPOS Monte Carlo generators. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Low-mass dielectron production in Pb–Pb collisions at √sNN = 2.76 TeV and feasibility of a QGP-temperature measurement

The main focus of research in the field of high-energy heavy-ion physics is the study of the quark-gluon plasma (QGP). Topic of the present work is the measurement of electron-positron pairs (dielectrons), which grant direct access to some of the key properties of this state of matter, since after their formation they leave the hot and dense medium without significant interaction. In particular, the measurement of the initial QGP temperature is considered a "holy grail" of heavy-ion physics. Therefore, in addition to the analysis of existing data, a feasibility study has been conducted to determine to which extent this goal would be achievable by upgrading the ALICE experiment at CERN. Dielectrons are produced during all stages of a heavy-ion collision, with their invariant mass reflecting the amount of energy available at the time of their formation. Dielectrons of highest mass are thus produced in the initial scatterings of the colliding nuclei by quark-antiquark annihilation. Correlated electron-positron pairs can also emerge from the decay chains of early-produced pairs of heavy-flavour (HF) particles. During the QGP stage and at the beginning of the hadronic phase, the system emits thermal radiation in the form of photons and dielectrons, which carry information about the medium temperature to the observer. In the final stage of the collision, decays of light-flavour (LF) hadrons produce additional contributions to the dielectron spectrum. The present work is based on early data from the ALICE experiment recorded from lead-lead collisions at a center-of-mass energy of 2.76 TeV. Due to the limited amount of data, a focus is placed on achieving high efficiencies throughout the analysis. To this end, a special electron identification strategy is developed and a custom track selection applied, together resulting in a tenfold increase in pair efficiency. The dielectron spectrum is evaluated on a statistical basis, using a pair prefilter, which is optimized based on two signal quality criteria, to reduce the fraction of electrons and positrons from unwanted sources at minimum signal loss. In addition, an artifact of the track reconstruction is exploited to suppress pairs from photon conversions and to correct the dielectron yield for a contribution from different-conversion pairs. The main signal uncertainty is extracted from the deviation between results of 20 analysis settings and amounts to 20% in most of the studied kinematic range. For comparison with the analysis results, a hadronic cocktail consisting of the LF and HF contributions is simulated, which can reasonably well describe the measured dielectron production, with a hint of an enhancement at low invariant mass. Two approaches to model the in-medium modification of the heavy-flavour are followed, resulting in up to 50% suppression, which creates some additional space for a thermal contribution at intermediate mass. For a complete comparison between experimental data and theoretical expectation, two model calculations are consulted. The Thermal Fireball Model provides predictions for thermal dielectron radiation from the QGP and hadron gas. The data tends to be better described with these additional thermal contributions. For a comparison with a prediction by the UrQMD model, the HF component of the cocktail is subtracted from the data. This results in better agreement if the HF suppression by in-medium effects is taken into account. The feasibility study in this work has served as a physical motivation for the ALICE upgrade for LHC Run 3. The precision with which the early temperature of the QGP can be determined via dielectrons is chosen as key observable. A multitude of individual contributions are merged into a fully modeled dielectron analysis. The resulting signal-to-background ratio represents some of the expected systematic uncertainties, while from the significance combined with the planned number of lead-lead collisions a realistic "measurement" with statistical fluctuations around the expected dielectron signal is generated using a Poisson sampling technique. Since the HF yield exceeds the QGP thermal radiation by about an order of magnitude, an additional analysis step exploiting the enhanced track reconstruction is introduced to reduce its contribution by up to a factor of five. The resulting reduction in pair efficiency is overcompensated by an up to hundred times higher collision rate. The entire cocktail is then subtracted from the sampled data to isolate the thermal excess yield. The final analysis of this spectrum shows that the inverse slope of the model prediction, which depends directly on the QGP temperature, can be reproduced within statistical and systematic uncertainties of about 10%. The promising results of this study have contributed on the one hand to the realization of the ALICE upgrade and to a design decision for the new Inner Tracking System, and at the same time represent exciting predictions for upcoming measurements.Der Forschungsschwerpunkt im Feld der Hochenergie-Schwerionenphysik liegt in der Studie des Quark–Gluon Plasmas (QGP). Thema der vorliegenden Arbeit ist die Messung von Elektron–Positron Paaren (Dielektronen), welche direkte Rückschlüsse auf zentrale Eigenschaften dieses Materiezustandes zulassen, da sie nach ihrer Entstehung das heiße und dichte Medium ohne nennenswerte Interaktionen verlassen. Insbesondere gilt die Messung der initialen Temperatur des QGP als ein “heiliger Gral” der Schwerionenphysik. Deshalb wurde zusätzlich zur Analyse bestehender Daten auch eine Machbarkeitsstudie durchgeführt, inwieweit dieses Ziel durch ein Upgrade des ALICE Experimentes am CERN erreichbar wird. Dielektronen werden in allen Stadien einer Schwerionenkollision produziert, wobei ihre invariante Masse die zum Zeitpunkt ihrer Erzeugung verfügbare Energie widerspiegelt. Somit werden die massereichsten Dielektronen in den initialen Nukleonenstößen durch Quark–Antiquark Annihilation erzeugt. Auch aus den Zerfallsreihen früh produzierter Paare schwerer Quarks, die als Heavy-Flavour (HF) bezeichnet werden, können korrelierte Elektron–Positron Paare hervorgehen. Während des QGP-Stadiums und zu Beginn der hadronischen Phase emittiert das System thermische Strahlung in Form von Photonen und Dielektronen, welche Informationen über die vorliegende Temperatur zum Beobachter tragen. Im Endstadium der Kollision erzeugen Zerfälle von Light-Flavour (LF) Hadronen zusätzliche Beiträge zum Dielektronenspektrum. Die vorliegende Arbeit basiert auf frühen Daten des ALICE Experimentes, die von Blei–Blei Kollisionen bei einer Schwerpunktsenergie von 2,76 TeV aufgezeichnet wurden. Aufgrund der geringen Datenmenge wird während der Analyse ein Fokus auf das Erreichen hoher Effizienzen gelegt. Dazu wird eine spezielle Strategie zur Elektronidentifizierung entwickelt sowie die Spurselektion angepasst, wodurch die Paareffizienz verzehnfacht werden kann. Das Dielektronenspektrum wird auf statistischer Basis ausgewertet, wobei eine anhand zweier Signalqualitätskriterien optimierte Vorabfilterung zur Reduktion des Anteils von Elektronen und Positronen aus unerwünschten Quellen verwendet wird. Zudem wird ein Artefakt der Spurrekonstruktion ausgenutzt, um Paare aus Photonkonversionen zu verwerfen und um eine Korrektur des Spektrums bei niedriger invarianter Masse vorzunehmen. Zum Vergleich mit den Ergebnissen der Datenanalyse wird ein hadronischer Cocktail bestehend aus den LF und HF Beiträgen simuliert, der die gemessene Dielektronenproduktion weitgehend gut beschreiben kann. Bei niedriger invarianter Masse zeigt sich teilweise eine geringe Erhöhung in den Daten und auch die eigens modellierte HF-Unterdrückung bei mittlerer Masse schafft etwas Raum für einen thermischen Beitrag. Für einen vollständigen Vergleich zwischen experimentellen Daten und theoretischer Erwartung werden Modellrechnungen hinzugezogen. Das Thermal Fireball Model liefert Vorhersagen für thermische Dielektronenstrahlung aus dem QGP und dem Hadrongas. Die Daten können mit den zusätzlichen thermischen Beiträgen teilweise besser beschrieben werden. Zum Vergleich mit einer Vorhersage des UrQMD Modells muss der HF Anteil des Cocktails von den Daten subtrahiert werden. Dabei ergibt sich eine bessere Übereinstimmung, wenn dessen Unterdrückung durch Medium-Effekte berücksichtigt wird. Für die Machbarkeitsstudie zur physikalischen Motiviation des ALICE Upgrades für LHC Run 3 wird als Kenngröße die Präzision gewählt, mit der die frühe Temperatur des QGP über Dielektronen bestimmt werden kann. Dazu wird eine Vielzahl individueller Beiträge zu einer vollwertig modellierten Dielektronenanalyse zusammengefasst. Das resultierende Signal-zu-Untergrund Verhältnis zeigt einen Teil der zu erwartenden systematischen Unsicherheiten auf, während aus der Signifikanz kombiniert mit der geplanten Anzahl an Blei–Blei Kollisionen eine realistische “Messung” mit statistischen Fluktuationen um das erwartete Dielektronensignal per Stichprobenerzeugung generiert wird. Da der HF etwa eine Größenordnung über der zu messenden thermischen Strahlung des QGP liegt, wird ein zusätzlicher Analyseschritt angewendet, der die verbesserte Spurrekonstruktion ausnutzt, um dessen Beitrag um bis zu einen Faktor fünf zu senken. Die dadurch stark reduzierte Paareffizienz kann durch eine bis zu hundertfache Kollisionsrate gut kompensiert werden. Der gesamte Cocktail wird dann von der generierten Messung subtrahiert, um das thermische Signal zu extrahieren. Bei der finalen Analyse dieses Spektrums zeigt sich, dass die inverse Steigung der Modellvorhersage, die direkt von der QGP-Temperatur abhängt, im Rahmen statistischer und systematischer Unsicherheiten von etwa 10% reproduziert werden kann. Die vielversprechenden Ergebnisse dieser Studie trugen einerseits zur Realisierung des ALICE Upgrades und zu einer Designentscheidung für das neue Inner Tracking System bei, und stellen zugleich spannende Vorhersagen für bevorstehende Messungen dar

Low-Mass Dielectron Production in Pb–Pb Collisions at sNN\sqrt{s_{\rm NN}} = 2.76 TeV and Feasibility of a QGP-Temperature Measurement

The main focus of research in the field of high-energy heavy-ion physics is the study of the quark-gluon plasma (QGP). Topic of the present work is the measurement of electron-positron pairs (dielectrons), which grant direct access to some of the key properties of this state of matter, since after their formation they leave the hot and dense medium without significant interaction. In particular, the measurement of the initial QGP temperature is considered a "holy grail" of heavy-ion physics. Therefore, in addition to the analysis of existing data, a feasibility study has been conducted to determine to which extent this goal would be achievable by upgrading the ALICE experiment at CERN. Dielectrons are produced during all stages of a heavy-ion collision, with their invariant mass reflecting the amount of energy available at the time of their formation. Dielectrons of highest mass are thus produced in the initial scatterings of the colliding nuclei by quark-antiquark annihilation. Correlated electron-positron pairs can also emerge from the decay chains of early-produced pairs of heavy-flavour (HF) particles. During the QGP stage and at the beginning of the hadronic phase, the system emits thermal radiation in the form of photons and dielectrons, which carry information about the medium temperature to the observer. In the final stage of the collision, decays of light-flavour (LF) hadrons produce additional contributions to the dielectron spectrum. The present work is based on early data from the ALICE experiment recorded from lead-lead collisions at a center-of-mass energy of 2.76 TeV. Due to the limited amount of data, a focus is placed on achieving high efficiencies throughout the analysis. To this end, a special electron identification strategy is developed and a custom track selection applied, together resulting in a tenfold increase in pair efficiency. The dielectron spectrum is evaluated on a statistical basis, using a pair prefilter, which is optimized based on two signal quality criteria, to reduce the fraction of electrons and positrons from unwanted sources at minimum signal loss. In addition, an artifact of the track reconstruction is exploited to suppress pairs from photon conversions and to correct the dielectron yield for a contribution from different-conversion pairs. The main signal uncertainty is extracted from the deviation between results of 20 analysis settings and amounts to 20% in most of the studied kinematic range. For comparison with the analysis results, a hadronic cocktail consisting of the LF and HF contributions is simulated, which can reasonably well describe the measured dielectron production, with a hint of an enhancement at low invariant mass. Two approaches to model the in-medium modification of the heavy-flavour are followed, resulting in up to 50% suppression, which creates some additional space for a thermal contribution at intermediate mass. For a complete comparison between experimental data and theoretical expectation, two model calculations are consulted. The Thermal Fireball Model provides predictions for thermal dielectron radiation from the QGP and hadron gas. The data tends to be better described with these additional thermal contributions. For a comparison with a prediction by the UrQMD model, the HF component of the cocktail is subtracted from the data. This results in better agreement if the HF suppression by in-medium effects is taken into account. The feasibility study in this work has served as a physical motivation for the ALICE upgrade for LHC Run 3. The precision with which the early temperature of the QGP can be determined via dielectrons is chosen as key observable. A multitude of individual contributions are merged into a fully modeled dielectron analysis. The resulting signal-to-background ratio represents some of the expected systematic uncertainties, while from the significance combined with the planned number of lead-lead collisions a realistic "measurement" with statistical fluctuations around the expected dielectron signal is generated using a Poisson sampling technique. Since the HF yield exceeds the QGP thermal radiation by about an order of magnitude, an additional analysis step exploiting the enhanced track reconstruction is introduced to reduce its contribution by up to a factor of five. The resulting reduction in pair efficiency is overcompensated by an up to hundred times higher collision rate. The entire cocktail is then subtracted from the sampled data to isolate the thermal excess yield. The final analysis of this spectrum shows that the inverse slope of the model prediction, which depends directly on the QGP temperature, can be reproduced within statistical and systematic uncertainties of about 10%. The promising results of this study have contributed on the one hand to the realization of the ALICE upgrade and to a design decision for the new Inner Tracking System, and at the same time represent exciting predictions for upcoming measurements

A Dual-Species Atom Interferometer Payload for Operation on Sounding Rockets

We report on the design and the construction of a sounding rocket payload capable of performing atom interferometry with Bose-Einstein condensates of K and Rb. The apparatus is designed to be launched in two consecutive missions with a VSB-30 sounding rocket and is qualified to withstand the expected vibrational loads of 1.8 g root-mean-square in a frequency range between 20-2000 Hz and the expected static loads during ascent and re-entry of 25 g. We present a modular design of the scientific payload comprising a physics package, a laser system, an electronics system and a battery module. A dedicated on-board software provides a largely automated process of predefined experiments. To operate the payload safely in laboratory and flight mode, a thermal control system and ground support equipment has been implemented and will be presented. The payload presented here represents a cornerstone for future applications of matter wave interferometry with ultracold atoms on satellites