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We report the design and characterization of a CMOS pixel direct charge sensor, Topmetal-II -, fabricated in a standard 0.35 µm CMOS Integrated Circuit process. The sensor utilizes exposed metal patches on top of each pixel to directly collect charge. Each pixel contains a low-noise charge-sensitive preamplifier to establish the analog signal and a discriminator with tunable threshold to generate hits. The analog signal from each pixel is accessible through time-shared multiplexing over the entire array. Hits are read out digitally through a column-based priority logic structure. Tests show that the sensor achieved a < 15 e − analog noise and a 200 e − minimum threshold for digital readout per pixel. The sensor is capable of detecting both electrons and ions drifting in gas. These characteristics enable its use as the charge readout device in future Time Projection Chambers without gaseous gain mechanism, which has unique advantages in low background and low rate-density experiments.

Two-particle angular correlations were measured in pp collisions at √ s = 7 TeV for pions, kaons, protons, and lambdas, for all particle/anti-particle combinations in the pair. Data for mesons exhibit an expected peak dominated by effects associated with mini-jets and are well reproduced by general purpose Monte Carlo generators. However, for baryon-baryon and anti-baryon-anti-baryon pairs, where both particles have the same baryon number, a near-side anticorrelation structure is observed instead of a peak. This effect is interpreted in the context of baryon production mechanisms in the fragmentation process. It currently presents a challenge to Monte Carlo models and its origin remains an open question.

The production of beauty hadrons was measured via semi-leptonic decays at mid-rapidity with the ALICE detector at the LHC in the transverse momentum interval 1 < p T < 8 GeV/c in minimum-bias p-Pb collisions at √ s NN = 5.02 TeV and in 1.3 < p T < 8 GeV/c in the 20% most central Pb-Pb collisions at √ s NN = 2.76 TeV. The pp reference spectra at √ s = 5.02 TeV and √ s = 2.76 TeV, needed for the calculation of the nuclear modification factors R pPb and R PbPb , were obtained by a pQCD-driven scaling of the cross section of electrons from beauty-hadron decays measured at √ s = 7 TeV. In the p T interval 3 < p T < 8 GeV/c, a suppression of the yield of electrons from beauty-hadron decays is observed in Pb-Pb compared to pp collisions. Towards lower p T , the R PbPb values increase with large systematic uncertainties. The R pPb is consistent with unity within systematic uncertainties and is well described by theoretical calculations that include cold nuclear matter effects in p-Pb collisions. The measured R pPb and these calculations indicate that cold nuclear matter effects are small at high transverse momentum also in Pb-Pb collisions. Therefore, the observed reduction of R PbPb below unity at high p T may be ascribed to an effect of the hot and dense medium formed in Pb-Pb collisions. Keywords: Heavy Ion ExperimentsArXiv ePrint: 1609.03898Open Access, Copyright CERN, for the benefit of the ALICE Collaboration. Article funded by SCOAP 3 .https://doi.org/10.1007/JHEP07(2017)052 The ALICE collaboration 33 JHEP07(2017)052 IntroductionIn collisions of heavy nuclei at ultra-relativistic energies, a high-density colour-deconfined state of strongly-interacting matter, called Quark-Gluon Plasma (QGP), is expected to be produced [1,2]. Due to their large masses (m Q Λ QCD ), heavy quarks (charm and beauty) are almost exclusively produced in the early stage of the collision via hard parton scatterings characterised by production-time scales of less than 0.1 and 0.01 fm/c for charm and beauty quarks, respectively [3]. They can, therefore, serve as probes to test the mechanisms of medium-induced parton energy loss, because the formation time of the QGP medium is expected to be about 0.3 fm/c [4] and its decoupling time is about 10 fm/c for collisions at LHC energies [5]. Due to their stronger colour coupling to the medium gluons are argued to lose more energy than quarks [6][7][8]. Furthermore, the radiative energy loss of heavy quarks is predicted to be reduced with respect to light quarks due to the massdependent restriction of the phase space into which medium-induced gluon radiation can take place (dead-cone effect) [9][10][11][12]. The effect of the charm-quark mass on energy loss becomes negligible at high transverse momentum, p T 10 GeV/c, where the ratio m c /p T approaches zero [13]. Therefore, due to the larger mass, beauty quarks can be sensitive -1 - JHEP07(2017)052probes for testing the mass dependence of the parton energy loss up to transverse momenta well above 10 GeV/c [13]. Final-state effects, such ...

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