The design of detectors used for experiments in high-energy physics requires a light, stiff, and efficient cooling system with a low material budget. The use of silicon microchannel cooling plates has gained considerable interest in the last decade. In this study, we propose the development of silicon microchannel cooling frames studied within the framework of the major upgrade of the Inner Tracking System (ITS) of the ALICE experiment at CERN. The preliminary results obtained with these frames demonstrate that they can withstand the internal pressure arising from the flow of the coolant with a limited mass penalty.

Measurements of inclusive and direct photon production at midrapidity in pp collisions at root s = 2.76 and 8 TeV are presented by the ALICE experiment at the LHC. The results are reported in transverse momentum ranges of 0.4 < p(T) < 10 GeV/c and 0.3 < p(T) < 16 GeV/c, respectively. Photons are detected with the electromagnetic calorimeter (EMCal) and via reconstruction of e(+) e(-) pairs from conversions in the ALICE detector material using the central tracking system. For the final measurement of the inclusive photon spectra the results are combined in the overlapping p(T), interval of both methods. Direct photon spectra, or their upper limits at 90% C.L. are extracted using the direct photon excess ratio R-gamma, which quantifies the ratio of inclusive photons over decay photons generated with a decay-photon simulation. An additional hybrid method, combining photons reconstructed from conversions with those identified in the EMCal, is used for the combination of the direct photon excess ratio R-gamma, as well as the extraction of direct photon spectra or their upper limits. While no significant signal of direct photons is seen over the full p(T), range, R-gamma, for p(T), > 7 GeV/c is at least one sigma above unity and consistent with expectations from next-to-leading order pQCD calculations.

The ALICE Collaboration , Acharya , S , Brücken , E J , Chang , B , Hilden , T E , Kim , D J , Litichevskyi , V , Mieskolainen , M M , Orava , R , Parkkila , J E , Rak , J , Räsänen , S S , Saarinen , S , Slupecki , M , Snellman , T W , Trzaska , W H , Vargyas , M & Viinikainen , J 2019 , ' Multiplicity dependence of light-flavor hadron production in pp collisions at root s=7 TeV ' , Physical Review C , vol. 99 , no. 2 , 024906 . https://doi.org/10.1103/PhysRevC.99.024906

Femtoscopic correlations between charged pions and kaons for different charge combinations are measured in Pb-Pb collisions at root s(NN) = 2.76 TeV with ALICE at the LHC. The three-dimensional pion-kaon (pi - K) correlation functions and double ratios in the out-side-long pair rest frame are studied in different centrality bins. The pi - K femtoscopic source size parameter (R-out) and emission asymmetry (mu(out)) are extracted. It is observed that the average source size of the system and the emission asymmetry between pions and kaons increase from peripheral to central events.

Thermal cooling performances of extremely lightweight mechanical carbon fiber support structures with an integrated liquid cooling system for monolithic silicon pixel detectors have been investigated. The high heat removal efficiency using single-phase liquid flow is shown for a power density up to 0.5 W/cm2. These solutions provide therefore possibility to build a detector with a record radiation length of 0.3% per layer, ensuring considerable extensions of the physical program of investigations of the quark-gluon plasma in ultra-relativistic heavy-ion collisions at the Large Hadron Collider.

Neutral pion and η meson invariant differential yields were measured in non-single diffractive p–Pb collisions at √ s NN = 5.02 TeV with the ALICE experiment at the CERN LHC. The analysis combines results from three complementary photon measurements, utilizing the PHOS and EMCal calorimeters and the Photon Conversion Method. The invariant differential yields of π 0 and η meson inclusive production are measured near mid-rapidity in a broad transverse momentum range of 0 . 3 < p T < 20 GeV / c and 0 . 7 < p T < 20 GeV / c , respectively. The measured η/π 0 ratio increases with p T and saturates for p T > 4 GeV / c at 0 . 483 ± 0 . 015 stat ± 0 . 015 sys . A deviation from m T scaling is observed for p T < 2 GeV / c . The measured η/π 0 ratio is consistent with previous measurements from proton-nucleus and pp collisions over the full p T range. The measured η/π 0 ratioathigh p T alsoagreeswithinuncertaintieswithmeasure-ments from nucleus–nucleus collisions. The π 0 and η yields in p–Pb relative to the scaled pp interpolated reference, R pPb , are presented for 0 . 3 < p T < 20 GeV / c and 0 . 7 < p T < 20 GeV / c , respectively. The results are compared with theoretical model calculations. Thevalues of R pPb areconsistent with unity for transverse momenta above 2 GeV / c . These results support the interpretation

Acharya, S.; Acosta, F.T.; Adamova, D.; Adolfsson, J; Aggarwal, MM.; Aglieri Rinella, G.; Agnello, Maria; Agrawal, N.; Ahammed, Z.; Ahn, S.U.; Aiola, S.; Akindinov, A.; Al-Turany, M.; Alam, SN; Albuquerque, DSD; Aleksandrov, D.; Alessandro, B; Molina, Rafael A.; Ali, Yusuf; Alici, A.; Alkin, A.; Alme, J.; Alt, T.; Bearden, Ian; bsm989, bsm989; Bilandzic, Ante; Gajdosova, Katarina; Gaardhøje, Jens Jørgen; Bourjau, Christian Alexander; Ozelin De Lima Pimentel, Lais; Thoresen, Freja; Nielsen, Børge Svane; Zhou, You; Chojnacki, Marek; Christensen, Christian Holm

The production yield of the Λ(1520) baryon resonance is measured at midrapidity in Pb-Pb collisions at sNN = 2.76 TeV with the ALICE detector at the Large Hadron Collider (LHC). The measurement is performed in the Λ(1520)→pK− (and charge conjugate) hadronic decay channel as a function of the transverse momentum (pT) and collision centrality. The ratio of the pT-integrated production of Λ(1520) baryons relative to Λ baryons in central collisions is suppressed by about a factor of 2 with respect to peripheral collisions. This is the first observation of the suppression of a baryonic resonance at the LHC and the first 3σ evidence of Λ(1520) suppression within a single collision system. The measured Λ(1520)/Λ ratio in central collisions is smaller than the value predicted by the statistical hadronization model calculations. The shape of the measured pT distribution and the centrality dependence of the suppression are reproduced by the EPOS3 Monte Carlo event generator. The measurement adds further support to the formation of a dense hadronic phase in the final stages of the evolution of the fireball created in heavy-ion collisions, lasting long enough to cause a significant reduction in the observable yield of short-lived resonances.

The transverse momentum distributions of the strange and double-strange hyperon resonances ( (cid:3)( 1385 ) ± , (cid:4)( 1530 ) 0 ) produced in p–Pb collisions at √ s NN = 5 . 02 TeV were measured in the rapidity range − 0 . 5 < y CMS < 0 for event classes corresponding to different charged-particle multiplicity densities, (cid:3) d N ch /d η lab (cid:4) . The mean transverse momentumvaluesarepresentedasafunctionof (cid:3) d N ch /d η lab (cid:4) , as well as a function of the particle masses and compared with previous results on hyperon production. The integrated yield ratios of excited to ground-state hyperons are constant as a function of (cid:3) d N ch /d η lab (cid:4) . The equivalent ratios to pions exhibit an increase with (cid:3) d N ch /d η lab (cid:4) , depending on their strangeness content.

A detailed study of pseudorapidity densities and multiplicity distributions of primary charged particles produced in proton–proton collisions, at √ s = 0.9, 2.36, 2.76, 7 and 8 TeV, in the pseudorapidity range |η| < 2, was carried out using the ALICE detector. Measurements were obtained for three event classes: inelastic, non-single diffractive and events with at least one charged particle in the pseudorapidity interval |η| < 1. The use of an improved track-counting algorithm combined with ALICE’s measurements of diffractive processes allows a higher precision compared to our previous publications. A KNO scaling study was performed in the pseudorapidity intervals |η| < 0.5, 1.0 and 1.5. The data are compared to other experimental results and to models as implemented in Monte Carlo event generators PHOJET and recent tunes of PYTHIA6, PYTHIA8 and EPOS.