Net-charge fluctuations in Pb-Pb collisions at sqrt[sNN]=2.76 TeV

We report the first measurement of the net-charge fluctuations in Pb-Pb collisions at sqrt[sNN]=2.76  TeV, measured with the ALICE detector at the CERN Large Hadron Collider. The dynamical fluctuations per unit entropy are observed to decrease when going from peripheral to central collisions. An additional reduction in the amount of fluctuations is seen in comparison to the results from lower energies. We examine the dependence of fluctuations on the pseudorapidity interval, which may account for the dilution of fluctuations during the evolution of the system. We find that the fluctuations at the LHC are smaller compared to the measurements at the BNL Relativistic Heavy Ion Collider, and as such, closer to what has been theoretically predicted for the formation of a quark-gluon plasma.

Longitudinal in vivo imaging of bone formation and resorption using fluorescence molecular tomography

Bone research often focuses on anatomical imaging of the bone microstructure, but in order to gain better understanding in how bone remodeling is modulated through interventions also bone formation and resorption processes should be investigated. With this in mind, the purpose of this study was to establish a longitudinal in vivo imaging approach of bone formation and resorption using fluorescence molecular tomography (FMT). In this study the reproducibility, accuracy and sensitivity of FMT for bone imaging were assessed by performing longitudinal measurements with FMT and comparing it to in vivo micro-computed tomography on a set of control mice, and mice in which load-adaptation was induced in the sixth caudal vertebra. The precision error for FMT measurements, expressed as coefficient of variation, was smaller than 16%, indicating acceptable reproducibility. A correlation was found between bone resorption measured with FMT and bone resorption rate measured with in vivo micro-computed tomography only over the first 14days (R=0.81, p<0.01), but not between bone formation measured with FMT and bone formation rate measured with in vivo micro-CT. Bone formation measured by FMT was 89-109% greater (p<0.05) for mice subjected to mechanical loading than control mice. Bone resorption was 5-8% lower, but did not reach a significant difference between groups, indicating moderate sensitivity for FMT. In conclusion, in vivo FMT in mouse tail bones is feasible but needs to be optimized for monitoring load adaptation in living mice.

Charge separation relative to the reaction plane in Pb-Pb collisions at sqrt[s(NN)] = 2.76 TeV

Measurements of charge-dependent azimuthal correlations with the ALICE detector at the LHC are reported for Pb-Pb collisions at sqrt[s(NN)] = 2.76 TeV. Two- and three-particle charge-dependent azimuthal correlations in the pseudorapidity range |η| < 0.8 are presented as a function of the collision centrality, particle separation in pseudorapidity, and transverse momentum. A clear signal compatible with a charge-dependent separation relative to the reaction plane is observed, which shows little or no collision energy dependence when compared to measurements at RHIC energies. This provides a new insight for understanding the nature of the charge-dependent azimuthal correlations observed at RHIC and LHC energies.

Pion, kaon, and proton production in central Pb-Pb collisions at sqrt[s(NN)] = 2.76 TeV

In this Letter we report the first results on π(±), K(±), p, and p production at midrapidity (|y|<0.5) in central Pb-Pb collisions at sqrt[s(NN)] = 2.76 TeV, measured by the ALICE experiment at the LHC. The p(T) distributions and yields are compared to previous results at sqrt[s(NN)] = 200 GeV and expectations from hydrodynamic and thermal models. The spectral shapes indicate a strong increase of the radial flow velocity with sqrt[s(NN)], which in hydrodynamic models is expected as a consequence of the increasing particle density. While the K/π ratio is in line with predictions from the thermal model, the p/π ratio is found to be lower by a factor of about 1.5. This deviation from thermal model expectations is still to be understood.

Measurement of the cross section for electromagnetic dissociation with neutron emission in Pb-Pb collisions at sqrt[s(NN)] = 2.76 TeV

The first measurement of neutron emission in electromagnetic dissociation of ^{208}Pb nuclei at the LHC is presented. The measurement is performed using the neutron zero degree calorimeters of the ALICE experiment, which detect neutral particles close to beam rapidity. The measured cross sections of single and mutual electromagnetic dissociation of Pb nuclei at sqrt[s(NN)]=2.76 TeV with neutron emission are σ(singleEMD)=187.4 ± 0.2(stat)(-11.2)(+13.2) (syst) b and σ(mutualEMD) = 5.7 ± 0.1(stat) ± 0.4(syst) b, respectively. The experimental results are compared to the predictions from a relativistic electromagnetic dissociation model.

Production of muons from heavy flavor decays at forward rapidity in pp and Pb-Pb collisions at sqrt[s(NN)]=2.76 TeV

The ALICE Collaboration has measured the inclusive production of muons from heavy-flavor decays at forward rapidity, 2.5<y<4, in pp and Pb-Pb collisions at sqrt[s(NN)]=2.76  TeV. The p(t)-differential inclusive cross section of muons from heavy-flavor decays in pp collisions is compared to perturbative QCD calculations. The nuclear modification factor is studied as a function of p(t) and collision centrality. A weak suppression is measured in peripheral collisions. In the most central collisions, a suppression of a factor of about 3-4 is observed in 6<p(t)<10  GeV/c. The suppression shows no significant p(t) dependence.

J/ψ suppression at forward rapidity in Pb-Pb collisions at √s(NN) = 2.76 TeV

The ALICE experiment has measured the inclusive J/ψ production in Pb-Pb collisions at √s(NN) = 2.76 TeV down to zero transverse momentum in the rapidity range 2.5 < y < 4. A suppression of the inclusive J/ψ yield in Pb-Pb is observed with respect to the one measured in pp collisions scaled by the number of binary nucleon-nucleon collisions. The nuclear modification factor, integrated over the 0%-80% most central collisions, is 0.545 ± 0.032(stat) ± 0.083(syst) and does not exhibit a significant dependence on the collision centrality. These features appear significantly different from measurements at lower collision energies. Models including J/ψ production from charm quarks in a deconfined partonic phase can describe our data.

Particle-yield modification in jetlike azimuthal dihadron correlations in Pb-Pb collisions at √s(NN)=2.76 TeV

The yield of charged particles associated with high-p(t) trigger particles (8<p(t)<15 GeV/c) is measured with the ALICE detector in Pb-Pb collisions at √s(NN)=2.76 TeV relative to proton-proton collisions at the same energy. The conditional per-trigger yields are extracted from the narrow jetlike correlation peaks in azimuthal dihadron correlations. In the 5% most central collisions, we observe that the yield of associated charged particles with transverse momenta p(t)>3 GeV/c on the away side drops to about 60% of that observed in pp collisions, while on the near side a moderate enhancement of 20%-30% is found.

J/ψ polarization in pp collisions at √s=7 TeV

The ALICE Collaboration has studied J/ψ production in pp collisions at √s=7 TeV at the LHC through its muon pair decay. The polar and azimuthal angle distributions of the decay muons were measured, and results on the J/ψ polarization parameters λ(θ) and λ(φ) were obtained. The study was performed in the kinematic region 2.5<y<4, 2<p(t)<8 GeV/c, in the helicity and Collins-Soper reference frames. In both frames, the polarization parameters are compatible with zero, within uncertainties.

OT2-05-01: An Open-Label Positron Emission Tomography Study To Investigate and Quantify Brain and Tumor Penetration of Carbon-11-Labeled Lapatinib in Patients with HER2−Overexpressing Advanced or Metastatic Breast Cancer

Background: Patients with HER2−overexpressing (HER2+) breast cancer tend to develop visceral metastases. About a third will develop brain metastases in the course of their disease. Several anticancer agents including trastuzumab are not believed to readily cross the blood-brain barrier (BBB); therefore, central nervous system (CNS) disease progression is emerging as an important clinical problem in this patient population. Although preclinical data indicate that lapatinib brain concentrations are low in healthy animals, probably due to the BBB efflux transporters, observations from clinical studies suggest lapatinib treatment might be associated with reduced CNS tumor growth. One hypothesis is that disruption of the BBB by tumors circumvents the usual protective function of transporters. Alternatively, inhibition of efflux transporters by lapatinib enhances its own accumulation with repeat dosing. The role of lapatinib in prevention of brain metastases is currently being explored in a phase III trial, EGF 111438 (CEREBEL).

Methods: To directly assess if lapatinib penetrates the brain and brain metastases, an open-label non-randomized study using carbon-11-labeled [11C] lapatinib is enrolling patients with HER2+ metastatic breast cancer. A minimum of 10 patients with an ECOG of &lt;3 are grouped into 2 cohorts: with at least one 1-cm diameter brain metastasis or without brain metastases. Two positron emission tomography (PET) scans will be performed in each patient following intravenous administration of a microdose of [11C] lapatinib: in lapatinib-naïve patients and at steady-state lapatinib, after treatment with unlabelled oral lapatinib 1500 mg once daily for 8 days. [11C] lapatinib time-activity curves will be generated for normal brain and brain metastases, the PET volume of distribution in the brain calculated and penetration of [11C] lapatinib into the brain quantified. Analysis of brain PET data is explorative as [11C] lapatinib is a new tracer. Therefore, this study investigates both the difference in lapatinib brain penetration between patients with and without brain metastases, as well as the effect of low and high concentrations of lapatinib on the BBB efflux system.

The study is currently recruiting in one center in the United Kingdom.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr OT2-05-01.

Higher harmonic anisotropic flow measurements of charged particles in Pb-Pb collisions at sqrt(s(NN)) = 2.76 TeV

We report on the first measurement of the triangular v3, quadrangular v4, and pentagonal v5 charged particle flow in Pb-Pb collisions at sqrt(s(NN)) = 2.76  TeV measured with the ALICE detector at the CERN Large Hadron Collider. We show that the triangular flow can be described in terms of the initial spatial anisotropy and its fluctuations, which provides strong constraints on its origin. In the most central events, where the elliptic flow v2 and v3 have similar magnitude, a double peaked structure in the two-particle azimuthal correlations is observed, which is often interpreted as a Mach cone response to fast partons. We show that this structure can be naturally explained from the measured anisotropic flow Fourier coefficients.