Zhou Z.,CAS Institute of Chemistry |
Zhou Z.,University of Chinese Academy of Sciences |
Hollingsworth J.V.,CAS Institute of Chemistry |
Hong S.,Beijing University of Chemical Technology |
And 2 more authors.
Langmuir | Year: 2014
Rheological measurements are utilized to examine the yielding behavior of a polystyrene (PS) core and poly(N-isopropylacrylamide) (PNIPAM) shell microgel system with varying shell/core ratio. For a shell/core ratio of 0.15 at high concentrations, the suspensions show a typical hard sphere (HS) yielding response where the loss modulus (G″) exhibits a single peak due to cage breaking. As a result of tighter cages and less cage distortion prior to yielding, the peak location of G″ decreases with volume fraction. For a shell/core ratio of 1.10, which behaves like a soft jammed glass at high concentration, the suspensions exhibit a one-step yielding behavior similar to that of HS glass. However, the location of the peak in G″ increases with volume fraction, demonstrating the important role of particle deformation in the breakage of cages. For an intermediate shell/core ratio of 0.34, the system displays a two-step yielding behavior, as observed in previous reports for attractive glasses. By increasing the volume fraction, the strain of the first peak increases while the second one decreases. In addition, as the effective volume fraction increases to 112%, the two peaks merge into one broad peak. It is demonstrated that the first peak of G″ is due to deformation of the shell, and the second peak of G″ is attributed to cage breaking as a result of the cores colliding with each other. Combining these results, a yielding state diagram from typical HS to soft jammed glass is demonstrated. © 2014 American Chemical Society.
News Article | February 19, 2016
After a century, scientists found direct evidence of gravitational waves from a collision of two black holes through the Large Interferometer Gravitational Wave Observatory (LIGO). This groundbreaking discovery encouraged Chinese scientists to investigate gravitational waves. The waves, described by scientists as a ripple in the invisible fabric of the universe, were proposed by Albert Einstein in 1916. The confirmation of the theory could transform how humans look at the world and outer space. Chinese physicists said that undertaking investigative projects in gravitational wave research would give China the opportunity to take the lead in the field. "If we launch our own satellites, we will have a chance to be a world leader in gravitational wave research in the future," says physicist Hu Wenrui, a member of the Chinese Academy of Sciences (CAS). The CAS proposed a space-based gravitational wave detector project called "Taiji." This program aims to give scientists a wider spectrum and more scientific data on gravitational waves produced by binary black holes. Under the Taiji program, China would be taking a 20 percent share of the European Space Agency's eLISA initiative or launch its own satellites into orbit by 2033. In July 2015, Sun Yat-sen University proposed its own project, "Tianqin," to launch three satellites into space to search for gravitational waves and investigate other cosmic mysteries. The Institute of High Energy Physics plans to implement a land-based project in Tibet. The project, called "Ali," entails detecting primordial gravitational waves, or the first tremors of the Big Bang. "Ali will be the first project detecting primordial gravitational waves in the sky above the Northern Hemisphere," says Su Meng, a Chinese researcher at the Massachusetts Institute of Technology Department of Physics. "If it succeeds, it will be the next milestone in cosmology as well as high energy physics." Though promising, all three projects are still awaiting approval and funding from the government. Wang Yifang, head of the CAS high-energy physics institute, is calling for improved scientific support. He says that though Chinese scientists contributed to the discovery of gravitational waves, the lack of funding and support hindered projects. The lack of support from the government and strict regulations on funding resulted in scientists giving up on international research projects, including the one with LIGO. "For example, under the current conditions, no authority is responsible for granting funding for research projects with budgets between 40 million yuan ($6.13 million) to 300 million yuan ($46 million)," Wang says. More than 90 percent of funding for research is given to prioritized domestic projects.
Deng Z.Y.,Institute of High Energy Physics |
Li W.D.,Institute of High Energy Physics |
Lin L.,Soochow University of China |
Liu H.M.,Institute of High Energy Physics |
And 4 more authors.
Journal of Physics: Conference Series | Year: 2012
The BES III detector is a new spectrometer which works on the upgraded high-luminosity collider, BEPCII. The BES III experiment studies physics in the tau-charm energy region from 2 GeV to 4.6 GeV . From 2009 to 2011, BEPCII has produced 106M ψ(2S) events, 225M J/ψ events, 2.8 fb-1 ψ(3770) data, and 500 pb-1 data at 4.01 GeV. All the data samples were processed successfully and many important physics results have been achieved based on these samples. Doing data production correctly and efficiently with limited CPU and storage resources is a big challenge. This paper will describe the implementation of the experiment-specific data production for BESIII in detail, including data calibration with event-level parallel computing model, data reconstruction, inclusive Monte Carlo generation, random trigger background mixing and multi-stream data skimming. Now, with the data sample increasing rapidly, there is a growing demand to move from solely using a local cluster to a more distributed computing model. A distributed computing environment is being set up and expected to go into production use in 2012. The experience of BESIII data production, both with a local cluster and with a distributed computing model, is presented here. © Published under licence by IOP Publishing Ltd.
It was a triumph for particle physics — and many were keen for a piece of the action. The discovery of the Higgs boson in 2012 using the world’s largest particle accelerator, the Large Hadron Collider (LHC), prompted a pitch from Japanese scientists to host its successor. The machine would build on the LHC’s success by measuring the properties of the Higgs boson and other known, or soon-to-be-discovered, particles in exquisite detail. But the next steps for particle physics now seem less certain, as discussions at the International Conference on High Energy Physics (ICHEP) in Chicago on 8 August suggest. Much hinges on whether the LHC unearths phenomena that fall outside the standard model of particle physics — something that it has not yet done but on which physicists are still counting — and whether China’s plans to build an LHC successor move forward. When Japanese scientists proposed hosting the International Linear Collider (ILC), a group of international scientists had already drafted its design. The ILC would collide electrons and positrons along a 31-kilometre-long track, in contrast to the 27-kilometre-long LHC, which collides protons in a circular track that is based at Europe’s particle-physics laboratory, CERN (See 'World of colliders'). Because protons are composite particles made of quarks, collisions create a mess of debris. The ILC's particles, by contrast, are fundamental and so provide the cleaner collisions more suited to precision measurements, which could reveal deviations from expected behaviour that point to physics beyond the standard model. For physicists, the opportunity to carry out detailed study of the Higgs boson and the heaviest, ‘top’ quark, the second most recently discovered particle, is reason enough to build the facility. Japan’s Ministry of Education, Culture, Sports, Science and Technology (MEXT) was expected to make a call on whether to host the project — which could begin experiments around 2030 — in 2016. But the Japanese panel advising MEXT indicated last year that opportunities to study the Higgs boson and the top quark would not on their own justify building the ILC, and that it would wait until the end of the LHC's first maximum-energy run – scheduled for 2018 – before making a decision. That means the panel is not yet convinced by the argument that the ILC should be built irrespective of what the LHC finds, says Masanori Yamauchi, director-general of Japan’s High Energy Accelerator Research Organization (KEK) in Tsukuba who sat on an ICHEP panel at a session on future facilities. “That’s the statement hidden under their statement,” he says. If the LHC discovers new phenomena, these would be further fodder for ILC study — and would strengthen the case for building the high precision machine. US physicists have long backed building a linear collider. And a joint MEXT and US Department of Energy group is discussing ways to reduce the ILC’s costs, says Yamauchi, which are now estimated at US$10 billion. A reduction of around 15% is feasible — but Japan will need funding commitments from other countries before it formally agrees to host, he added. Snapping at Japan’s heels is a Chinese team. In the months after the Higgs discovery, a team of physicists led by Wang Yifang, director of the Institute of High Energy Physics in Beijing, floated a plan to host a collider in the 2030s, also partially funded by the international community and focused on precision measurements of the Higgs and other particles. Circular rather than linear, this 50–100-kilometre-long electron–positron smasher would not reach the energies of the ILC. But it would require the creation of a tunnel that could allow a proton–proton collider — similar to the LHC, but much bigger — to be built at a hugely reduced cost. Wang and his team this year secured around 35 million yuan (US$5 million) in funding from China’s Ministry of Science and Technology to continue research and development for the project, Wang told the ICHEP session. Last month, China’s National Development and Reform Commission turned down a further request from the team for 800 million yuan, but other funding routes remain open, Wang said, and the team now plans to focus on raising international interest in the project. By affirming worldwide interest in Higgs physics, the Chinese proposal bolsters Japan’s case for building the ILC, says Yamauchi. But if it goes ahead, it could drain international funding from the ILC and put its future on shakier ground. “It may have a negative impact,” he says. In the future, the option to use China's electron–positron collider as the basis for a giant proton–proton collider could interfere with CERN’s own plans for a 100-kilometre-circumference circular machine that would smash protons together at more than 7 times the energy of the LHC. Until the mid-2030s, CERN will be busy with an upgrade that will raise the intensity — but not the energy — of the LHC’s proton beam. And by that time, China might have a suitable tunnel that could make it harder to get backing for this ‘super-LHC’. At ICHEP, Fabiola Gianotti, CERN’s director-general, floated an interim idea: souping up the energy of the LHC beyond its current design by installing a new generation of superconducting magnets by around 2035. This would provide a relatively modest boost in energy — from 14 teraelectronvolts (TeV) to 28 TeV — that would have a strong science case if the LHC finds new physics at 14 TeV, said Gianotti. Its $5-billion price tag could be paid for out of CERN’s regular budget. For decades, successive facilities have found particles predicted by the standard model, and neither the LHC nor any of its proposed successors is guaranteed to find new physics. Questions asked at the ICHEP session revealed some soul-searching among attendees, including a plea to reassure young high-energy physicists about the future of the field and contemplation of whether money would be better spent on other approaches rather than ever-bigger accelerators. Indeed, the US is betting on neutrinos, fundamental particles that could reveal physics beyond the standard model, not colliders. The Fermi National Accelerator Laboratory (Fermilab) in Batavia, Illinois, hopes to become the world capital of neutrino physics by hosting the $1-billion Long-Baseline Neutrino Facility, which will beam neutrinos to a range of detectors starting in 2026. Funding will require approval from US Congress in 2017. But at the ICHEP session, Fermilab director Nigel Lockyer was confident: “We are beyond the point of no return. It is happening.”
Louvot R.,Ecole Polytechnique Federale de Lausanne |
Schneider O.,Ecole Polytechnique Federale de Lausanne |
Aushev T.,Institute of Theoretical and Experimental Physics |
Arinstein K.,RAS Budker Institute of Nuclear Physics |
And 131 more authors.
Physical Review Letters | Year: 2010
First observations of the Bs0→Ds*-π+, Bs0→Ds-ρ+ and Bs0→Ds*-ρ+ decays are reported together with measurements of their branching fractions: B(Bs0→Ds*-π+)=[2.4-0.4+0.5(stat)±0.3(syst) ±0.4(fs)]×10-3, B(Bs0→Ds-ρ+)=[8.5-1. 2+1.3(stat)±1.1(syst)±1.3(fs)]×10-3 and B(Bs0→Ds*-ρ+)=[11.9-2.0+2.2(stat)±1.7(syst) ±1.8(fs)]×10-3 (fs=NBs(*)B̄s(*)/ Nbb̄). From helicity-angle distributions, we measured the longitudinal polarization fraction in Bs0→Ds*-ρ+ decays to be fL(Bs0→Ds*-ρ+)=1.05-0.10+0.08(stat)-0.04+0.03(syst). These results are based on a 23.6fb-1 data sample collected at the Υ(5S) resonance with the Belle detector at the KEKB e+e - collider. © 2010 The American Physical Society.