CMS physics technical design report : Addendum on high density QCD with heavy ions

Peer reviewe

Distribution and composition of loess sediments in the Ili Basin, Central Asia

Loess deposits in Central Asia provide an important record of regional climate and environmental change. However, in contrast to the intensively investigated loess deposits on the Chinese Loess Plateau (CLP), loess sediments in the Ili Basin of eastern Central Asia are poorly understood. Based on field investigation and existing literature, this paper presents a preliminary study of the distribution, strata and composition of the Ili loess. The distribution of the Ili loess is clearly controlled by topographic and geomorphic conditions, mainly in the river terraces, low uplands, and slopes of the Tianshan Mountains. The thickness of the loess varies from several meters to over two hundred meters. To characterize the Ili loess composition, the authors analyzed its grain size, geochemistry, X-ray diffraction pattern and heavy mineral assemblage. Grain size analyses reveal that the Ili loess consists predominantly of silt (4-63 mu m) with a minor proportion of sand, which is coarser than the loess of the CLP and suggests a nearby provenance. The bulk mineral components of the Ili loess are dominated by quartz and feldspar with minor amounts of calcite, chlorite, mica, dolomite and hornblende. More than 20 types of heavy minerals were observed with major components of amphibole, magnetite and epidote. The major elements of the Ili loess are characterized by high abundance of SiO2, Al2O3 and CaO and minor amounts of Fe2O3, MgO, Na2O and K2O. Compared to the CLP loess, the Ili loess is relatively rich in Na2O and displays higher Na2O/Al2O3 ratios, suggesting weak weathering. The distribution patterns of REEs indicate that both the Ili loess and CLP loess are of typical upper crustal composition, with enrichment in LREE, negative Eu anomalies, and depletion of HREE. Both the heavy mineral assemblage and geochemistry indicate that the local bedrock of the Ili Basin may have contributed only a little to the loess sediments.</p

Timing and Spatial Distribution of Loess inXinjiang, NW China

Central Asia is one of the most significant loess regions on Earth, with an important role in understanding Quaternary climate and environmental change. However, in contrast to the widely investigated loess deposits in the Chinese Loess Plateau, the Central Asian loess– paleosol sequences are still insufficiently known and poorly understood. Through field investigation and review of the previous literature, the authors have investigated the distribution, thickness and age of the Xinjiang loess, and analyzed factors that control these parameters in the Xinjiang in northwest China, Central Asia. The loess sediments cover river terraces, low uplands, the margins of deserts and the slopes of the Tianshan Mountains and Kunlun Mountains and are also present in the Ili Basin. The thickness of the Xinjiang loess deposits varies from several meters to 670 m. The variation trend of the sand fraction (>63 μm) grain-size contour can indicate the local major wind directions, so we conclude that the NW and NE winds are the main wind directions in the North and South Xinjiang, and the westerly wind mainly transport dust into the Ili basin. We consider persistent drying, adequate regional wind energy and well-developed river terraces to be the main factors controlling the distribution, thickness and formation age of the Xinjiang loess. The well-outcropped loess sections have mainly developed since the middle Pleistocene in Xinjiang, reflecting the appearance of the persistent drying and the present air circulation system. However, the oldest loess deposits are as old as the beginning of the Pliocene in the Tarim Basin, which suggests that earlier aridification occurred in the Tarim Basin rather than in the Ili Basin and the Junggar Basin

Paleomagnetic and Fission-Track Dating of a Late Cenozoic Red Earth Section in the Liupan Shan and Associated Tectonic Implications

The north-trending Liupan Shan is an important tectonic boundary between the Tibetan Plateau and the Ordos platform. The Late Cenozoic red earth deposits of the Liupan Shan record its tectonic history and environmental effects. In this article we report a new Late Cenozoic red earth section from an intermontane basin in the southern part of the Liupan Shan. Lithofacies analysis, paleomagnetic and fission-track chronologies, and paleocurrent analysis have been employed to identify the tectonic uplift events of the Liupan Shan. Based on the age constraints of mammal fossils, the paleomagnetic polarity zones of the Huating Section can be approximately correlated with the standard polarity zones that lie between C3An.2n and C5n.1n of the Geomagnetic Polarity Timescale; the bottom age of this section is approximately 10 Ma. Based on this and the previous studies, we infer that a tectonic event commenced in the southern Liupan Shan in this interval between 8.3 and 8.7 Ma, accompanied by a remarkable increase in sediment accumulation rate. Field observations, fission-track dating, determinations of grain-size frequency distributions and the vertebrate fossils found there suggest that the red earth deposits were reworked by water and mainly transported by fluvial-alluvial processes from the adjacent area.</p

Comparison between luminescence and radiocarbon dating of lateQuaternary loess from the Ili Basin in Central Asia

Dust depositions are critical archives for understanding interior aridification and westerly climatic changes in Central Asia. Accurate and reliable dating of loess is very important for interpreting and correlating environmental records. There remains a disparity between luminescence ages and radiocarbon dating of late Quaternary loess from the Ili Basin in Central Asia. In this study, we establish a closely spaced quartz optically stimulated luminescence (OSL) chronology for the 20.5-m-thick Nilka loess section in the Ili Basin. Based on OSL ages, two intervals of higher mass accumulation rate occurred at 49&ndash;43&nbsp;ka and 24&ndash;14&nbsp;ka. We further compare these OSL ages with 23 accelerator mass spectrometry (AMS) 14C ages of bulk organic matter. The results indicate that the OSL and radiocarbon ages agree well for ages younger than ca. 25 14C cal&nbsp;ka&nbsp;BP. However, beyond 30&nbsp;cal&nbsp;ka&nbsp;BP, there is no consistent increase in AMS 14C age with depth, while the OSL ages continue to increase. These differences confirm the observation that the AMS 14C ages obtained using conventional acid&ndash;base&ndash;acid (ABA) pretreatment are severely underestimated in other terrestrial deposits in Central Asia, which could be due to 2&ndash;4% modern carbon contamination. However, OSL dating is applicable for constructing an accurate chronology beyond 30&nbsp;cal&nbsp;ka&nbsp;BP. We suggest caution when interpreting paleoenvironmental changes based on radiocarbon ages older than 25&nbsp;cal&nbsp;ka&nbsp;BP.</p

CMS physics technical design report: Addendum on high density QCD with heavy ions

This report presents the capabilities of the CMS experiment to explore the rich heavy-ion physics programme offered by the CERN Large Hadron Collider (LHC). The collisions of lead nuclei at energies ,will probe quark and gluon matter at unprecedented values of energy density. The prime goal of this research is to study the fundamental theory of the strong interaction - Quantum Chromodynamics (QCD) - in extreme conditions of temperature, density and parton momentum fraction (low-x). This report covers in detail the potential of CMS to carry out a series of representative Pb-Pb measurements. These include "bulk" observables, (charged hadron multiplicity, low pT inclusive hadron identified spectra and elliptic flow) which provide information on the collective properties of the system, as well as perturbative probes such as quarkonia, heavy-quarks, jets and high pT hadrons which yield "tomographic" information of the hottest and densest phases of the reaction.0info:eu-repo/semantics/publishe

Measurement of the production cross section for a W boson and two b jets in pp collisions at root s=7 TeV

The production cross section for a Wboson and two b jets is measured using proton-proton collisions at v root s = 7 TeV in a data sample collected with the CMS experiment at the LHC corresponding to an integrated luminosity of 5.0 fb(-1). The W + bbevents are selected in the W..decay mode by requiring a muon with transverse momentum pT> 25GeVand pseudorapidity |eta| 25GeVand |eta| < 2.4. The measured W + bbproduction cross section in the fiducial region, calculated at the level of final-state particles, is s(pp. W + bb) xB(W..) = 0.53 +/- 0.05 (stat.) +/- 0.09 (syst.) +/- 0.06 (theo.) 0.01 (lum.) pb, in agreement with the standard model prediction. In addition, kinematic distributions of the W + bbsystem are in agreement with the predictions of a simulation usingMadGraphandpythia