Search

Many future particle colliders require beam crabbing to recover geometric luminosity loss from the nonzero crossing angle at the interaction point (IP). A first demonstration experiment of crabbing with hadron beams was successfully carried out with high energy protons. This breakthrough result is fundamental to achieve the physics goals of the high luminosity LHC (HL-LHC) and the future circular collider (FCC). The expected peak luminosity gain (related to collision rate) is 65% for HL-LHC and even greater for the FCC. Novel beam physics experiments with proton beams in CERN’s Super Proton Synchrotron (SPS) were performed to demonstrate several critical aspects for the operation of crab cavities in the future HL-LHC including transparency with a pair of cavities, a full characterization of the cavity impedance with high beam currents, controlled emittance growth from crab cavity induced rf noise. This research is supported by the HL-LHC project, US Department of Energy and UK Science and Technology Council through HL-LHC-UK. The authors thank the members of HL-LHC WP4 (crab cavity) Collaboration and CERN departments for their invaluable contributions. A special acknowledgement to the CARE, EuCARD, and US-LHC Accelerator Research Program (LARP) for their important role in enabling this research during the R&D phase. We also acknowledge the contributions of KEKB and Niowave Inc. to the crab cavity R&D.

Synchrotron radiation (SR) originated at superconducting bending magnets is known to be at the origin of several beam detrimental effects related to vacuum instabilities. One of the major challenges in the design of the vacuum beam pipes of high-energy hadron colliders is the SR coping strategy. In the case of the future circular hadron collider (FCC-hh), a Cu-coated beam screen (BS) operating in the range of 40–60 K has been designed with the aim of protecting the superconducting magnet cold bores from direct synchrotron irradiation. In order to experimentally study the FCC-hh BS vacuum and cryogenic performance, two sample prototypes were manufactured and installed in the beam screen test-bench experiment (BESTEX) at the Karlsruhe Research Accelerator (KARA) at the Karlsruhe Institute of Technology (KIT). The emitted SR has a critical energy of 6.2 keV, very similar to the 4.6 keV of FCC-hh. Irradiation at both room (RT) and cryogenic (77 K) temperatures showed a significant reduction of the molecular photostimulated desorption yields (η) of the FCC-hh beam screen compared to those of Cu samples. A first approximation of η and its evolution with the photon dose accumulated on the FCC-hh BS prototype at 77 K allows to estimate that a machine conditioning period of ∼1.2 months would be needed to reduce the photostimulated molecular density at the necessary levels to ensure a 100 h beam lifetime at nominal FCC-hh operation.

EuroCirCol is a conceptual design study of a post-LHC, Future Circular Hadron Collider (FCC-hh) which aims to expand the current energy and luminosity frontiers. The vacuum chamber of this 100 TeV, 100 km collider, will have to cope with unprecedented levels of synchrotron radiation linear power for proton colliders, 160 times higher than in the LHC for baseline parameters, releasing consequently much larger amounts of gas into the system. At the same time, it will be dealing with a tighter magnet aperture. In order to reach a good vacuum level, it has been necessary to find solutions beyond the particle colliders' state of art. This paper proposes a design of a novel beam screen, the element responsible for absorbing the emitted power. It is intended to overcome the drawbacks derived from the stronger synchrotron radiation while allowing at the same time a good beam quality.

EuroCirCol is a conceptual design study of a post-LHC, Future Circular Hadron Collider (FCC-hh) with 50 TeV of beam energy and 100 km long, which aims to expand the current energy and luminosity frontiers. The vacuum chamber of the FCC-hh will have to cope with unprecedented levels of synchrotron radiation power for proton colliders, dealing simultaneously with a tighter magnet aperture. Considering that the high radiation power and photon flux will release larger amounts of gas into the system, the difficulty to meet the vacuum specifications increases substantially compared with the LHC. This paper presents a study on the beam induced vacuum effects for the FCC-hh novel conditions, the different phenomena which, owing to the presence of the beam, have an impact on the accelerator's vacuum level. It is concluded that thanks to the adopted mitigation measures the proposed vacuum system shall be adequate, allowing us to reach $\ensuremath{\le}1\ifmmode\times\else\texttimes\fi{}{10}^{15}\text{ }\text{ }{\mathrm{H}}_{2\text{ }eq}/{\mathrm{m}}^{3}$ with baseline beam parameters within the first months of conditioning.

The Large Hadron Collider (LHC), currently under operation at CERN, is colliding intense proton beams at the highest energy frontier up to ∼14 TeV in the centre of mass. This superconducting storage ring is at the origin of the discovery in 2012 of the so-called ‘Higgs’ Boson explaining the origin of the mass of weak bosons W + ,W − and Z also discovered at CERN in 1983. The arc vacuum system, which operates at cryogenic temperatures, consists of a 1.9 K cold bore which houses a 5–20 K beam screen. Beam collisions are performed inside a Non-Evaporable-Getter coated vacuum system located in long straight sections held at room temperature. These vacuum systems were designed to be stable under ion bombardment, to cope with intense VUV synchrotron radiation flux and to mitigate beam induced multipacting effects. In this paper, the LHC beam vacuum system design is recalled. Its operation, challenges and achieved performances during the commissioning phase will be discussed in detail.

Evaluated nuclear structure and decay data for all nuclides with mass number A=183 (Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb) are presented here. At, Po and Fr have not yet been observed, but for prediction of ground state and/or isomer properties see, e.g., 2015Bh08 (At, Fr), 2013Ba41 (Tl), 2013Ho05 (Po). This evaluation includes structure and decay data information available by 15 April 2015 and supersedes that by R.B. Firestone published in Nuclear Data Sheets 65, 589 (1992) (literature cutoff 9 January 1991), and subsequent revisions by C.M. Baglin for 183Au in ENSDF database (literature cutoff 13 March 1999), 183Hg in Nuclear Data Sheets 91, 117 (2000) (literature cutoff 25 September 2000), 183Tl in Nuclear Data Sheets 95, 49 (2002) (literature cutoff 1 January 2002) and 183Pb in ENSDF (literature cutoff 6 January 2003). Since the prior Nuclear Data Sheets publication of this mass chain: 183Yb (2012Ku26) and 183Pb (2006An11, 2006Se18, 2007De09, 2009Se13) have been observed; our knowledge of high–spin states has been significantly expanded for 183Ta (2009Sh17), 183W (1999Sa60), 183Re (1998Ha51, 2001Sh41), 183Au (2002Jo18, 2005So01) and 183Tl (2001Mu26, 2004Ra28); a large amount of new structure information for 183W has been obtained from transfer reactions (1997Pr02, 2011Bo09), (n,n'γ) (1993Pr09) and thermal neutron capture (1993Pr09, 1997Pr02, 2011Bo09, 2014Hu02), as well as from the two–photon cascade study by 2005Su29.

The evaluated spectroscopic data are presented for 11 known nuclides of mass 211 (Hg, Tl, Pb, Bi, Po, At, Rn, Fr, Ra, Ac, Th). The 211 Pa nuclide is included here but its identification remains uncertain. For 211 Hg, 211 Tl, 211 Ac and 211 Th nuclei, only the ground–state information is available. Their decay characteristics are mostly unknown. 211 Fr is suggested to decay partially through e decay mode, but its decay scheme remains poorly known. While high–spin excitations, including several isomers, are well studied in 211 Pb, 211 Bi, 211 Po, 211 At, 211 Rn and 211 Fr, the particle–transfer data are available for only 211 Po and 211 Bi. This evaluation was carried out as part of joint IAEA–ICTP workshop for Nuclear Structure and Decay Data, organized and hosted by the IAEA, Vienna and ICTP, Trieste, August 6–17, 2012. This work supersedes previous A=211 evaluation (2004Br45) published by E. Browne which covered literature before January 2003.

Experimental structure and decay data for all nuclei with mass A=192 (Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl, Pb, Bi, Po, At) have been evaluated. This evaluation, covering data received by 15 June 2012, supersedes the 1998 evaluation by C. M. Baglin (Nuclear Data Sheets 84, 717 (1998), literature cutoff August 1998) and the subsequent inclusion in the ENSDF database of the new nuclide 192At (C. M. Baglin, literature cutoff 16 May 2006). It also incorporates the current evaluation of superdeformed-band information by B. Singh. Since the last publication, 192Ta, 192W and 192At have been observed, and an isomeric state has been identified in 192Re. The e decay of 192Au has been studied using a multidetector array resulting in an extensively revised level scheme for 192Pt.

The CERN Large Hadron Collider (LHC) has 54 km of ultra-high vacuum (UHV) beam chambers out of which about 90% are at cryogenic temperature (1.9 K) and the rest at room temperature. During operation, the residual gas density in the beam pipes is dominated by beam induced effect such ion, electron and photon-stimulated gas desorption. Therefore, the computation of gas density profile is of great importance to confirm the vacuum stability, and to estimate the beam lifetime. Moreover, the gas density profiles are essential to determine the machine induced background in the experimental areas, and to define the pressure profile in the cryogenic sectors where there is no vacuum instrumentation available. In this paper, the vacuum stability is studied for a newly proposed upgrade of the vacuum chamber at the ATLAS interaction point, using the vacuum stability code called VASCO. The residual gas density profile along the ATLAS vacuum chambers and the effects of photon and electron flux hitting the vacuum chamber walls are presented and analysed.

The outgassing rate of the collimators in the Large Hadron Collider (LHC) at CERN has an important role for the life-time of the Non-Evaporable Getter (NEG), and an accurate analysis allows the definition of future activities, like NEG vacuum activation. For these reasons, both, total outgassing rate and gas composition of a secondary collimator have been measured in the laboratory. The outgassing rate decreases by about two orders of magnitude by after bake-out and moreover, repeated bake-out further reduced the outgassing rate. The gas transmission through the NEG coated beam pipes and the resulting pressure distributions near the collimator were also measured in a dedicated setup. It is found that the main gas component after just 2 m of NEG coated beam pipe is CH 4 due to the extreme pumping speed of NEG for the other gases. Large amount of outgassing for H 2 and carbon related molecules are released when moving the collimator jaws. It is found that the NEG is very effective even in such case with large gas load.

Abstract: Nuclear structure data pertaining to all nuclei with mass number Au93 have been complied and evaluated and incorporated into the ENSDP data file. General Policies and Organization of Material: See the January issue of Nuclear Data Sheets. General Comments: This publication for A=93 supercedes the previous (full) publication Ch. Sievers, Nuclear Data Sheets 54, 99 (1988)) and the subsequent update (C. Baglin, Nuclear Data Sheets 70, 1 (1993)). It includes all literature available prior to November 1, 1996. Cutoff Date: This evaluation includes all data available prior to November 1, 1996. Acknowledgments: The advice and assistance received from B. Singh (McMaster University), who reviewed the material added to the A=93 mass chain since its 1993 revision, are gratefully acknowledged. The authors also wishes to thank R. Helmer for provision and helpful discussion of the prepublication data contained in references 96GrZZ and 96GrZY. Throughout this evaluation, the energy adopted for a level exited only in reactions in which γ rays have not been measured is the weighted average of all energies which can be associated uniquely with that level. Uncertainties in absolute γ ray intensities have been calculated using the method of Browne (86Br2I), where relevant. Adopted E γ and I γ data for which the source is not specified are weighted averages of all the available data.

Nuclear structure data pertaining to all nuclei with mass A=168 (Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt) have been evaluated and incorporated into the ENSDF data file. This evaluation supersedes the previous publication (V.S. Shirley, Nuclear Data Sheets 71, 261 (1994) (literature cutoff date July 1993)) and subsequent ENSDF file revisions for Tb and Dy (C. Baglin, literature cutoff date of 15 June 1999) and Hf (B. Singh, literature cutoff date of 30 April 2001), and includes literature available by 15 June 2010. Since the above evaluations, the first excited states in {sup 168}Pt have been identified (1998Ki20, 2009Go16) and {alpha} decay from {sup 172}Hg has been observed (2009Sa27, 2004Ke06, 1999Se14). New levels in {sup 168}Dy have been excited using the {sup 170}Er({sup 82}Se,{sup 84}Kr{gamma}) reaction (2010So03). (HI,xn{gamma}) studies have significantly expanded our knowledge of level structure in {sup 168}Lu (1999Ka17, 2002Ha33), {sup 168}Ta (2008QiZZ), {sup 168}Yb (1995Fi01), {sup 168}Tm (2007CaZW), {sup 168}Hf (2009Ya21), {sup 168}Os (2001Jo11, 2009Od02) and, for {sup 168}Tm, important information has come also from (d,2n{gamma}) and ({alpha},n{gamma}) reactions (1995Si20). Revised decay schemes are available following new studies of {sup 168}Hf {epsilon} decay (6.7 min) (1997Ba26), {sup 168}Lu {epsilon} decaymore » (1999Ba65), {sup 168}Ta {epsilon} decay (2007Mc08) and {sup 172}Au {alpha} decay (2009Ha42). Significant new information for {sup 168}Er is available from (p,t) (2006Bu09), (d,p) and (t,d) (1996Ma50), ({gamma},{gamma}') (1996Ma18), (136Xe, X{gamma}) (2010Dr02), ({sup 238}U,{sup 238}U{sup '{gamma}}) (2003Wu07) and (n,n{sup '{gamma}}) (1998Be20, 1998Be62) reactions, and the availability of {gamma}{gamma} coin data (1994Ju02, 1996Gi09) for the (n,{gamma}) E=thermal reaction has resulted in some significant level scheme revisions.« less

Nuclear structure data pertaining to all nuclei with mass number A = 179 (Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt, Au, Hg, Tl) have been compiled and evaluated, and incorporated into the ENSDF database. This evaluation for A = 179, which considers data available by 15 November 2008, supersedes the previous complete publication (E. Browne, Nuclear Data Sheets 55, 483 (1988), cutoff September 1987) and the update-mode publication (C. Baglin, Nuclear Data Sheets 72, 617 (1994), cutoff date September 1994), as well as the subsequent evaluations of Ta, Ir and Tl by C. Baglin (literature cutoff dates January 2000, October 1998 and February 2001, respectively). The newly evaluated literature provides new Coulomb excitation data for Hf, transfer reaction data for Hf and Ta, new information on Au and Hg from α decay and significant (HI,xnγ) reaction data for Hf, Ta, Re, Au and Hg. At the time of the 1994 evaluation, no γ-ray information was available for Au or Hg; that situation has now changed dramatically, although additional work on details of the low-lying structure of Au could be instructive.

Experimental data pertaining to all nuclei with mass number A = 169 (Dy, Ho, Er, Tm, Yb, Lu, Hf, Ta, W, Re, Os, Ir, Pt) have been evaluated. Level schemes from both radioactive decay and reaction studies are presented, along with associated tables of experimental data and adopted properties for levels and γ rays. These include data from several recent high-precision measurements of intensities for γ rays emitted in 169Yb e decay; these are of special interest because of their use as calibration standards. Excited-state information is newly available for Re, Os, Ir and Pt, and heavy-ion reaction studies have significantly expanded our knowledge of excited states in Lu through Ta. More extensive work on e decay from W is needed and new experimental work will be required to resolve a discrepancy between the Jπ values deduced for a 180-keV level in 169Ta based on extensive band structure from (HI,xnγ) work (Jπ = 1/2–) and TDPAD measurements (J = 5/2). The present evaluation for A = 169, which considers data received by 15 June 2008, supersedes the 1991 evaluation (with a literature cutoff date of March 1990) by V. Shirley, published in Nuclear Data Sheets 64, 505 (1991).

The 27 km long large hadron collider (LHC), currently under construction at CERN, will collide protons beam at 14 TeV in the centre of mass. In the 8 arcs, the superconducting dipoles and quadrupoles of the FODO cells operate with superfluid He at 1.9 K. In the 8 long straight sections, the cold bores of the superconducting magnets are held at 1.9 or 4.5 K. Thus, in the LHC, ∼75% of the beam tube vacuum chamber is cooled with He. In many areas of the machine, He leaks could appear in the beam tube. At cryogenic temperature, the gas condenses onto the cold bores or beam screens, and interacts with the circulating beam. He leaks creates a He front propagating along the vacuum chambers, which might cause magnet quench. We discuss the consequences of He leaks, the possible means of detections, the strategies to localise them and the methods to measure their size.

The production of $\rho$ , $\omega$ and $\phi$ vector-mesons, detected through their $\mu\mu$ decay channel, is studied in p-W, S-S, S-Cu and S-U reactions at 200 GeV/c per nucleon incident momentum. Their inclusive cross-sections are determined in various transverse momentum intervals and their dependence on the projectile and target mass numbers is investigated. The relative yield $B_{\mu\mu}\sigma_{\phi}/(B_{\mu\mu}\sigma_{\rho} + B_{\mu\mu}\sigma_{\omega})$ is measured, both as a function of the transverse momentum, pT, and of the collision centrality. While this ratio exhibits no significant dependence with pT, it clearly increases with the centrality of the collision. Effective temperatures deduced from the transverse mass spectra, $d\sigma/dM_T$ , lead to values of $T_{\rho + \omega}$ equal or slightly higher than $T_{\phi}$ . Both these effective temperatures smoothly increase from p-W to S-U reactions.

NA50; Angular distributions of charged particles produced in Pb-Pb collisions at the CERN SPS have been measured by the NA50 experiment. Measurements have been performed with a silicon microstrip detector at two different beam energies (40 and 158 GeV/nucleon) and over a wide impact parameter (centrality) range. The centrality of the collision has been evaluated both by neutral transverse energy released in the interaction and by spectator nucleons energy (zero degree energy). The charged particle density at midrapidity shows a linear dependence on the number of participating nucleons at both beam energies. The particle density per participant pair and its $\sqrt{S}$ dependence are also studied.

The cold bore experiment installed in the super proton synchrotron has been used to study the performance of a vacuum system operating at cryogenic temperatures in the presence of a large hadron collider (LHC) type proton beam. The ∼2 m long cryostat, which can be cooled below 3 K, is fitted with an actively cooled beam screen which can be temperature controlled between 5 and 100 K. Molecular desorption and deposited heat load measurements, with or without gas pre-condensation, have been performed. Implications to the LHC design and operation will be discussed.

From proton, deuteron, S- and Pb-induced reactions, experiments NA38 and NA50 have measured muon pair production with various targets. In particular, the production rates of the , ω and ρ mesons have been simultaneously extracted and compared. Preliminary partial results of the most recent Pb–Pb measurement done in year 2000 by NA50 are presented here. They are also included in the comparison with the results obtained with lighter interacting nuclei.

We present the measurements of charged particle pseudorapidity distributions dNch/dη performed by the NA50 experiment in Pb-Pb collisions at the CERN SPS. Measurements were done at incident energies of 40 GeV (√s = 8.77 GeV) and 158 GeV (√s = 17.3 GeV) per nucleon over a broad impact parameter range. The multiplicity distributions are studied as a function of centrality using the number of participating nucleons(N part ), or the number of binary nucleon-nucleon collisions (Ncoll). Their values at midrapidity exhibit a linear scaling withN part at both energies. Particle yield increases approximately by a factor of 2 betweeny √s = 8.77 GeV and √s = 17.3 GeV.

Nuclear structure data pertaining to all nuclei with mass number A=186 have been evaluated, and incorporated into the ENSDF database. This evaluation for A=186 includes data available by 4 April 2003. It supersedes the previous publication (C. Baglin, Nuclear Data Sheets 82, 1 (1997) (literature cutoff date 31 August 1997)) and subsequent revisions of Hf and Ta (literature cutoff date 26 November 1998) and W (literature cutoff date 17 February 1999).

Nuclear structure data pertaining to all nuclei with mass number A=170 have been compiled and evaluated, and incorporated into the ENSDF data file. This evaluation supersedes the previous evaluation (Coral M. Baglin, Nuclear Data Sheets 77, 125 (1996), cutoff date October 1995) and subsequent updates of the ENSDF file for Yb (cutoff 17 February 1999), Lu (cutoff 8 October 1998), Pt (cutoff 17 February 1999) and Ta (cutoff 7 April 1998). It includes all literature available by 15 August 2002.

The experiment NA50 studies the strangeness production by means of the BRμμσ/(BRρμμσρ + BRωμμσω) cross-sections ratio in relativistic heavy ion collisions with respect to proton and light ion collisions. New results for Pb+Pb interactions at 158 A GeV/c are presented (1998 data) and analysed with a different method. The BRμμσ/(BRρμμσρ + BRωμμσω) ratio shows an increase with the number of participants, in agreement with previous results. The inverse slope parameter extracted from the MT universal scaling is also studied.

The NA52 experiment searched for long-lived charged strangelets in 158 A GeV/c Pb+Pb collisions at CERN SPS. We collected 1013 Pb+Pb interactions looking for negatively charged strangelets and 3 × 1011 Pb+Pb interactions for positively charged ones. No evidence for the production of strangelets has been observed. The upper strangelet production limits are discussed. Besides the strangelet searches NA52 was able to identify particles and anti-particles over a wide range in rapidity. Results of the invariant differential particle production cross sections including fragments up to carbon and 5 are presented.

Experimental data pertaining to all nuclei with mass number A=59 have been evaluated. Level schemes from both radioactive decay and reaction studies are presented, along with associated tables of experimental data and adopted properties for levels and # rays. This evaluation for A=59, which considers data received by 8 February 2002, supersedes the 1993 evaluation (with a literature cutoff date of August 1993) by Coral M. Baglin, published in update mode in Nuclear Data Sheets 69, 733 (1993).

Abstract: Nuclear structure data pertaining to 183 Tl have been compiled and evaluated, and incorporated into the ENSDF data file. This evaluation of 183 Tl supersedes the previous publication (R.B. Firestone, Nuclear Data Sheets 65, 589 (1992) (literature cutoff date 9 January 1991)), and includes literature available by 1 January 2002. The newly incorporated references are: 2001Mu26, 2000Re04, 1999Ba45, 1998Ak04, 1995Au04, 1992BoZO, 1992BlZW, 1984ScZQ, 1980Sc09.

The NA52 experiment searches for long-lived charged strangelets in 158 A GeV c-1 Pb + Pb collisions at CERN SPS. The experiment is able to identify single particles coming from the collisions at pt = 0. We collected 1013 Pb + Pb interactions looking for negatively charged strangelets and 3 × 1011 Pb + Pb interactions for positively charged ones. No evidence for the production of strangelets has been observed. We present here resulting experimental differential and total upper production limits.

Nuclear structure data pertaining to all nuclides with mass number A=92 have been compiled and evaluated, and incorporated into the ENSDF data file. All literature available by 7 November 2000 has been considered. This evaluation supersedes the previous publication for this mass chain (Coral M. Baglin, Nuclear Data Sheets 66, 347 (1992) (May 1992 cutoff data)), and all subsequent unpublished reevaluations incorporated into the ENSDF file prior to the present work.

Nuclear structure data pertaining to 183 Hg have been compiled and evaluated, and incorporated into the ENSDF data file. This evaluation of 183 Hg supersedes the previous publication (R.B. Firestone, Nuclear Data Sheets 65 , 589 (1992) (literature cutoff date 9 January 1991)), and includes literature available by 25 September 2000. The newly incorporated references are: 1992BoZO, 1993Bi17, 1995Au04, 1995La10, 1995Sh04, 1999An10, 1999An36, 1999Ba45, 2000By02.

Experimental data pertaining to all nuclei with mass number A = 167 have been evaluated. Level schemes from both radioactive decay and reaction studies are presented, along with associated tables of experimental data and adopted properties for levels and γ rays. This evaluation for A = 167, which considers data received by 5 July 2000, supersedes the 1989 compilation by V. Shirley (1989Sh33), published in Nuclear Data Sheets 58, 871 (1989).

Low mass dimuons production has been studied in Pb-Pb collisions at 158 GeV/A . φ, ρ and ω contributions are extracted in different transverse mass and transverse energy domains. Preliminary results of the 1996 run display an increase of the φ/(ρ+ω) ratio, coming from an increase of the φ. Cross sections are presented and temperatures extracted.

The impact parameter dependence of π±, K±, p, p , d and d yields produced in fixed target lead+lead collisions at 158 A GeV incident energy is presented. The particle yields are measured near zero transverse momentum and in the forward rapidity region.

Besides the dedicated search for strangelets NA52 measures light (anti)particle and (anti)nuclei production over a wide range of rapidity. Compared to previous runs the statistics has been increased in the 1998 run by more than one order of magnitude for negatively charged objects at different spectrometer rigidities. At a rigidity of −20 GeV/c we measured 106 p , 103 d and one 3 He without any centrality requirements. These preliminary results together with previous measurements near central rapidity are discussed in the framework of a thermodynamical and a coalescence model.

Nuclear structure data pertaining to 181Pt have been compiled and evaluated, and incorporated into the ENSDF data file. This evaluation of 181Pt supersedes the previous publication (R. B. Firestone, Nuclear Data Sheets 62, 101 (1991) (literature cutoff date October 1990)), and includes literature available by 2 July 1999. New references since last publication: 1998RoZY, 1995Au04, 1993Me13, 1992Sa03 (supersedes 1990SaZU).

For the design of future accelerators, in particular, the beam vacuum of the large hadron collider (LHC), a 27 km circumference proton collider to be built at CERN, ‘white light’ (WL) and monochromatic VUV synchrotron radiation (SR) have been used to measure, both qualitatively and quantitatively, electron emission from candidate vacuum chamber materials. Emphasis has been placed on measuring the photoelectron yields (PY) and the energy distribution of the emitted electrons. These parameters are relevant to gas desorption, the LHC cryogenic cooling capacities and the possible creation of an electron cloud which may cause beam instabilities. Proposed materials, prepared on an industrial scale, such as 50 μm OFE Cu co-laminated onto a high Mn-content stainless steel, exhibit significant modifications when exposed to the WL spectrum from the BESSY TGM7 beamline. Surface cleaning treatments, such as sample annealing and ion bombardment, induce substantial changes to the electron emission which therefore indicate that such surfaces would not be constant, in terms of electron emission, during machine operation. Surfaces which are considered to be constant electron emitters, such as annealed TiZr alloys and commercial non-evaporable getters, were also investigated. These results and their implications for the choice of the material to be used for the LHC are discussed.

We present new results of the CERN experiment NA52 on the centrality dependence of π±, K±, p, d, and production yields near zero transverse momentum and at several rapidities, from 64% to 4% of the total Pb + Pb cross section. Baryon yields increase nearly linearly and K± yields faster than linearly with the number of participating nucleons Np. The antibaryon yields increase less than linearly with Np, indicating absorption. The centrality and rapidity dependence of the π−/π+ ratio indicates Coulomb interaction of the pions with the projectile spectator protons. Within the framework of a coalescence model the radius of the particle source has been estimated from the ratios d/p2 and /2. The source radii are similar for matter and antimatter and are found to increase with ~ Np0.30−0.36.

Nuclear structure data pertaining to 170 Lu have been compiled and evaluated, and incorporated into the ENSDF data file. This evaluation of 170 Lu supersedes the previous publication (C. Baglin, Nuclear Data Sheets 77, 125 (1996) (literature cutoff date October 1995)), and includes literature available by 8 Otober 1998.

We report on baryon and antibaryon as well as K+ and K− production cross sections measured in lead-lead collisions at 158 GeV /c per nucleon. The presented data were taken at zero degree production angle with a minimum bias trigger. The measurements covered a wide range of rapidity 1.4

The Drell-Yan and J ψ cross-sections measured in PbPb collisions are compared with the values extrapolated from the results obtained in proton and light ion induced reactions. While the Drell-Yan production exhibits the normal expected behaviour, the yield of J ψ in PbPb interactions is abnormally low, as it lies 9 standard deviations below the expected value. Moreover, the departure from the expected behaviour increases significantly from peripheral to central collisions.

We searched for long-lived strange quark matter particles, so-calledstrangelets, and studied particle and antiparticle production in Pb+Pb collisions at 158 GeV/c per nucleon at zero degree production angle. We give upper limits for the production of strangelets covering a mass to charge ratio up to 120 GeV/c 2 and lifetimest lab>1.2 μs and plot invariant differential production cross sections as a function of rapidity for a variety of particles.

The production of low mass dimuons has been measured in d-C, d-U and S-U collisions at 200 GeV per nucleon, and in Pb-Pb collisions at 160 GeV per nucleon. Theϕ, ρ andω productions in S-U collision [1, 2] are extracted from a new set of data with increased statistic, and are throughϕ/(ω+ρ) ratio compared to first results on deuteron induced production. These new analyses are presented in the limitedM T domain of recent Pb-Pb measurement whose preliminary results are also presented.

We searched for long-lived strange quark matter particles, so-called strangelets , and studied particle and antiparticle production in Pb + Pb collisions at 158 GeV/ c per nucleon at zero degree production angle. We give upper limits for the production of strangelets covering a mass to charge ratio up to 120 GeV/ c 2 and lifetimes t lab > 1.2 μ s and plot invariant differential production cross sections as a function of rapidity for a variety of particles.

The NA52 experiment searches for long-lived massive strange quark matter particles, so-called {ital strangelets}, produced in Pb-Pb collisions at a beam momentum of {ital p}{sub lab}=158 AGeV/{ital c}. Upper limits for the production of strangelets at zero degree production angle covering a mass to charge ratio up to 120 GeV/{ital c}{sup 2} and lifetimes {ital t}{sub lab}{approx_gt}1.2 {mu}s are given. The data presented here were taken during the 1994 lead beam running period at CERN. {copyright} {ital 1996 The American Physical Society.}

We investigate antinuclei production in Pb + Pb interactions at 158 GeV/ c per nucleon at zero degree production angle. We quote invariant differential production cross sections for antiprotons and antideuterons. The corresponding antideuteron to antiproton ratio at midrapidity is 4.2 · 10 −4 . One antihelium-3 nucleus was observed. The results are discussed in the framework of a simple coalescence model.

Muon pair production is studied in p-W and SU collisions at 200 GeV per nucleon, as a function of transverse momentum PTμμ. The inclusive ϱ+ω and Φ differential cross-sections dσ dP T are measured in the dimuon decay channel, for PT ≥ 0.6 GeV/c, in the central rapidity region, 3.0≤ y ≤ 4.0. Assuming the power law A-dependence σ = σ0(Abeam·Atarget)α, the study of the integrated cross-sections for p-W and SU collisions leads to αϱ+ω = 1.00±0.02±0.07 and αΦ = 1.23±0.03±0.05, showing clear evidence of Φ enhancement in SU interactions as compared to p-W collisions.

The transverse mass differential cross-sections for the ϱ + ω and Φ resonances is obtained, in the central rapidity region, in p - W and S  U interactions at 200 GeV/nucleon. The measured ϱ + ω and Φ temperatures are ∼ 15% higher in S  U as compared to p - W collisions. The ratio of cross-sections times branching ratios into the dimuon channel B Φ σ Φ (B ϱ σ ϱ + B ω σ ω ) is studied as a function of the energy density reached in the collision and of the dimuon transverse momentum. The measured ratio is 2 to 3 times larger in S  U than in p - W collisions and an enhancement is observed in S  U interactions with increasing energy density.