Tag Archives: lhcb

The mass difference spectrum: the LHCb result shows strong evidence of the existence of two new particles the Xi_b'- (first peak) and Xi_b*- (second peak), with the very high-level confidence of 10 sigma. The black points are the signal sample and the hatched red histogram is a control sample. The blue curve represents a model including the two new particles, fitted to the data. Delta_m is the difference between the mass of the Xi_b0 pi- pair and the sum of the individual masses of the Xi_b0 and pi-.. INSET: Detail of the Xi_b'- region plotted with a finer binning.
Credit: CERN

CERN makes public first data of LHC experiments

CERN1 launched today its Open Data Portal where data from real collision events, produced by the LHC experiments will for the first time be made openly available to all. It is expected that these data will be of high value for the research community, and also be used for education purposes.

”Launching the CERN Open Data Portal is an important step for our Organization. Data from the LHC programme are among the most precious assets of the LHC experiments, that today we start sharing openly with the world. We hope these open data will support and inspire the global research community, including students and citizen scientists,” said CERN Director General Rolf Heuer.

The principle of openness is enshrined in CERN’s founding Convention, and all LHC publications have been published Open Access, free for all to read and re-use. Widening the scope, the LHC collaborations recently approved Open Data policies and will release collision data over the coming years.

The first high-level and analysable collision data openly released come from the CMS experiment and were originally collected in 2010 during the first LHC run. This data set is now publicly available on the CERN Open Data Portal. Open source software to read and analyse the data is also available, together with the corresponding documentation. The CMS collaboration is committed to releasing its data three years after collection, after they have been thoroughly studied by the collaboration.

“This is all new and we are curious to see how the data will be re-used,” said CMS data preservation coordinator Kati Lassila-Perini. “We’ve prepared tools and examples of different levels of complexity from simplified analysis to ready-to-use online applications. We hope these examples will stimulate the creativity of external users.”

 The mass difference spectrum: the LHCb result shows strong evidence of the existence of two new particles the Xi_b'- (first peak) and Xi_b*- (second peak), with the very high-level confidence of 10 sigma. The black points are the signal sample and the hatched red histogram is a control sample. The blue curve represents a model including the two new particles, fitted to the data. Delta_m is the difference between the mass of the Xi_b0 pi- pair and the sum of the individual masses of the Xi_b0 and pi-.. INSET: Detail of the Xi_b'- region plotted with a finer binning. Credit: CERN
The mass difference spectrum: the LHCb result shows strong evidence of the existence of two new particles the Xi_b’- (first peak) and Xi_b*- (second peak), with the very high-level confidence of 10 sigma. The black points are the signal sample and the hatched red histogram is a control sample. The blue curve represents a model including the two new particles, fitted to the data. Delta_m is the difference between the mass of the Xi_b0 pi- pair and the sum of the individual masses of the Xi_b0 and pi-.. INSET: Detail of the Xi_b’- region plotted with a finer binning.
Credit: CERN

In parallel, the CERN Open Data Portal gives access to additional event data sets from the ALICE, ATLAS, CMS and LHCb collaborations, which have been specifically prepared for educational purposes, such as the international masterclasses in particle physics2 benefiting over ten thousand high-school students every year. These resources are accompanied by visualisation tools.

“Our own data policy foresees data preservation and its sharing. We have seen that students are fascinated by being able to analyse LHC data in the past and so, we are very happy to take the first steps and make available some selected data for education” said Silvia Amerio, data preservation coordinator of the LHCb experiment.

“The development of this Open Data Portal represents a first milestone in our mission to serve our users in preserving and sharing their research materials. It will ensure that the data and tools can be accessed and used, now and in the future,” said Tim Smith from CERN’s IT Department.

All data on OpenData.cern.ch are shared under a Creative Commons CC03 public domain dedication; data and software are assigned unique DOI identifiers to make them citable in scientific articles; and software is released under open source licenses. The CERN Open Data Portal is built on the open-source Invenio Digital Library software, which powers other CERN Open Science tools and initiatives.

Further information:

Open data portal

Open data policies

CMS Open Data

 

Footnote(s):

1. CERN, the European Organization for Nuclear Research, is the world’s leading laboratory for particle physics. It has its headquarters in Geneva. At present, its Member States are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Romania is a Candidate for Accession. Serbia is an Associate Member in the pre-stage to Membership. India, Japan, the Russian Federation, the United States of America, Turkey, the European Commission and UNESCO have Observer Status.

2. http://www.physicsmasterclasses.org(link is external)

3. http://creativecommons.org/publicdomain/zero/1.0/

The mass difference spectrum: the LHCb result shows strong evidence of the existence of two new particles the Xi_b'- (first peak) and Xi_b*- (second peak), with the very high-level confidence of 10 sigma. The black points are the signal sample and the hatched red histogram is a control sample. The blue curve represents a model including the two new particles, fitted to the data. Delta_m is the difference between the mass of the Xi_b0 pi- pair and the sum of the individual masses of the Xi_b0 and pi-.. INSET: Detail of the Xi_b'- region plotted with a finer binning.
Credit: CERN

LHCb experiment observes two new baryon particles never seen before

Geneva 19 November 2014. Today the collaboration for the LHCb experiment at CERN1’s Large Hadron Collider announced the discovery of two new particles in the baryon family. The particles, known as the Xi_b’- and Xi_b*-, were predicted to exist by the quark model but had never been seen before. A related particle, the Xi_b*0, was found by the CMS experiment at CERN in 2012. The LHCb collaboration submitted a paper reporting the finding to Physical Review Letters.

Like the well-known protons that the LHC accelerates, the new particles are baryons made from three quarks bound together by the strong force. The types of quarks are different, though: the new X_ib particles both contain one beauty (b), one strange (s), and one down (d) quark. Thanks to the heavyweight b quarks, they are more than six times as massive as the proton. But the particles are more than just the sum of their parts: their mass also depends on how they are configured. Each of the quarks has an attribute called “spin”. In the Xi_b’- state, the spins of the two lighter quarks point in the opposite direction to the b quark, whereas in the Xi_b*- state they are aligned. This difference makes the Xi_b*a little heavier.

“Nature was kind and gave us two particles for the price of one,” said Matthew Charles of the CNRS’s LPNHE laboratory at Paris VI University. “The Xi_b’is very close in mass to the sum of its decay products: if it had been just a little lighter, we wouldn’t have seen it at all using the decay signature that we were looking for.”

 The mass difference spectrum: the LHCb result shows strong evidence of the existence of two new particles the Xi_b'- (first peak) and Xi_b*- (second peak), with the very high-level confidence of 10 sigma. The black points are the signal sample and the hatched red histogram is a control sample. The blue curve represents a model including the two new particles, fitted to the data. Delta_m is the difference between the mass of the Xi_b0 pi- pair and the sum of the individual masses of the Xi_b0 and pi-.. INSET: Detail of the Xi_b'- region plotted with a finer binning. Credit: CERN
The mass difference spectrum: the LHCb result shows strong evidence of the existence of two new particles the Xi_b’- (first peak) and Xi_b*- (second peak), with the very high-level confidence of 10 sigma. The black points are the signal sample and the hatched red histogram is a control sample. The blue curve represents a model including the two new particles, fitted to the data. Delta_m is the difference between the mass of the Xi_b0 pi- pair and the sum of the individual masses of the Xi_b0 and pi-.. INSET: Detail of the Xi_b’- region plotted with a finer binning.
Credit: CERN

“This is a very exciting result. Thanks to LHCb’s excellent hadron identification, which is unique among the LHC experiments, we were able to separate a very clean and strong signal from the background,”said Steven Blusk from Syracuse University in New York. “It demonstrates once again the sensitivity and how precise the LHCb detector is.”

As well as the masses of these particles, the research team studied their relative production rates, their widths – a measure of how unstable they are – and other details of their decays. The results match up with predictions based on the theory of Quantum Chromodynamics (QCD).

QCD is part of the Standard Model of particle physics, the theory that describes the fundamental particles of matter, how they interact and the forces between them. Testing QCD at high precision is a key to refine our understanding of quark dynamics, models of which are tremendously difficult to calculate.

“If we want to find new physics beyond the Standard Model, we need first to have a sharp picture,” said LHCb’s physics coordinator Patrick Koppenburg from Nikhef Institute in Amsterdam. “Such high precision studies will help us to differentiate between Standard Model effects and anything new or unexpected in the future.”

The measurements were made with the data taken at the LHC during 2011-2012. The LHC is currently being prepared – after its first long shutdown – to operate at higher energies and with more intense beams. It is scheduled to restart by spring 2015.

Further information

Link to the paper on Arxiv: http://arxiv.org/abs/1411.4849(link is external)
More about the result on LHCb’s collaboration website: http://lhcb-public.web.cern.ch/lhcb-public/Welcome.html#StrBeaBa
Observation of a new Xi_b*0 beauty particle, on CMS’ collaboration website:http://cms.web.cern.ch/news/observation-new-xib0-beauty-particle

Footnote(s)

1. CERN, the European Organization for Nuclear Research, is the world’s leading laboratory for particle physics. It has its headquarters in Geneva. At present, its Member States are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Romania is a Candidate for Accession. Serbia is an Associate Member in the pre-stage to Membership. India, Japan, the Russian Federation, the United States of America, Turkey, the European Commission and UNESCO have Observer Status.

Source: CERN

The Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile has taken this beautiful image, dappled with blue stars, of one of the most star-rich open clusters currently known — Messier 11, also known as NGC 6705 or the Wild Duck Cluster. Credit: ESO

Discovery of new subatomic particle sheds light on fundamental force of nature

The discovery of a new particle will “transform our understanding” of the fundamental force of nature that binds the nuclei of atoms, researchers argue.

he Wide Field Imager on the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile has taken this beautiful image, dappled with blue stars, of one of the most star-rich open clusters currently known — Messier 11, also known as NGC 6705 or the Wild Duck Cluster. Credit: ESO
Along with gravity, the electromagnetic interaction and weak nuclear force, strong-interactions are one of four fundamental forces. Lead scientist Professor Tim Gershon, from The University of Warwick’s Department of Physics, explains:
“Gravity describes the universe on a large scale from galaxies to Newton’s falling apple, whilst the electromagnetic interaction is responsible for binding molecules together and also for holding electrons in orbit around an atom’s nucleus.”
Image Credit: ESO

Led by scientists from the University of Warwick, the discovery of the new particle will help provide greater understanding of the strong interaction, the fundamental force of nature found within the protons of an atom’s nucleus.

Named Ds3*(2860)ˉ, the particle, a new type of meson,[1] was discovered by analysing data collected with the LHCb detector at CERN’s Large Hadron Collider (LHC)[2]. The LHCb experiment, which is run by a large international collaboration, is designed to study the properties of particles containing beauty and charm quarks and has unique capability for this kind of discovery.

The new particle is bound together in a similar way to protons. Due to this similarity, the Warwick researchers argue that scientists will now be able to study the particle to further understand strong interactions.

Along with gravity, the electromagnetic interaction and weak nuclear force, strong-interactions are one of four fundamental forces. Lead scientist Professor Tim Gershon, from The University of Warwick’s Department of Physics, explains:

“Gravity describes the universe on a large scale from galaxies to Newton’s falling apple, whilst the electromagnetic interaction is responsible for binding molecules together and also for holding electrons in orbit around an atom’s nucleus.”

The strong interaction is the force that binds quarks, the subatomic particles that form protons within atoms, together. It is so strong that the binding energy of the proton gives a much larger contribution to the mass, through Einstein’s equation E = mc2, than the quarks themselves.[3]

Due in part to the forces’ relative simplicity, scientists have previously been able to solve the equations behind gravity and electromagnetic interactions, but the strength of the strong interaction makes it impossible to solve the equations in the same way.

“Calculations of strong interactions are done with a computationally intensive technique called Lattice QCD,” says Professor Gershon. “In order to validate these calculations it is essential to be able to compare predictions to experiments. The new particle is ideal for this purpose because it is the first known that both contains a charm quark and has spin 3.”

There are six quarks known to physicists; Up, Down, Strange, Charm, Beauty and Top. Protons and neutrons are composed of up and down quarks, but particles produced in accelerators such as the LHC can contain the unstable heavier quarks. In addition, some of these particles have higher spin values than the naturally occurring stable particles.

“Because the Ds3*(2860)ˉ particle contains a heavy charm quark it is easier for theorists to calculate its properties. And because it has spin 3, there can be no ambiguity about what the particle is,” adds Professor Gershon. “Therefore it provides a benchmark for future theoretical calculations. Improvements in these calculations will transform our understanding of how nuclei are bound together.”

Spin is one of the labels used by physicists to distinguish between particles. It is a concept that arises in quantum mechanics that can be thought of as being similar to angular momentum: in this sense higher spin corresponds to the quarks orbiting each other faster than those with a lower spin.

Warwick Ph.D. student Daniel Craik, who worked on the study, adds “Perhaps the most exciting part of this new result is that it could be the first of many similar discoveries with LHC data. Whether we can use the same technique, as employed with our research into Ds3*(2860)ˉ, to also improve our understanding of the weak interaction is a key question raised by this discovery. If so, this could help to answer one of the biggest mysteries in physics: why there is more matter than antimatter in the Universe.”

The results are detailed in two papers that will be published in the next editions of the journals Physical Review Letters and Physical Review D. Both papers have been given the accolade of being selected as Editors’ Suggestions.

[1] The Ds3*(2860)ˉ particle is a meson that contains a charm anti-quark and a strange quark. The subscript 3 denotes that it has spin 3, while the number 2860 in parentheses is the mass of the particle in the units of MeV/c2 that are favoured by particle physicists. The value of 2860 MeV/c2 corresponds to approximately 3 times the mass of the proton.

[2] The particle was discovered in the decay chain Bs0D0Kπ+ , where the Bs0, D0, K and π+ mesons contain respectively a bottom anti-quark and a strange quark, a charm anti-quark and an up quark, an up anti-quark and a strange quark, and a down anti-quark and an up quark. The Ds3*(2860)ˉ particle is observed as a peak in the mass of combinations of the D0 and K mesons. The distributions of the angles between the D0, K and π+ particles allow the spin of the Ds3*(2860)ˉ meson to be unambiguously determined.

[3] Quarks are bound by the strong interaction into one of two types of particles: baryons, such as the proton, are composed of three quarks; mesons are composed of one quark and one anti-quark, where an anti-quark is the antimatter version of a quark.

The results are detailed in papers titled:

- The LHCb experiment is one of the four main experiments at the CERN Large Hadron Collider, and is set up to explore what happened after the Big Bang that allowed matter to survive and build the Universe we inhabit today. The LHCb collaboration comprises about 700 physicists from 67 institutes in 17 countries.

- CERN, the European Organization for Nuclear Research, is the world’s leading laboratory for particle physics. It has its headquarters in Geneva. At present, its Member States are Austria, Belgium, Bulgaria, the Czech Republic, Denmark, Finland, France, Germany, Greece, Hungary, Israel, Italy, the Netherlands, Norway, Poland, Portugal, Slovakia, Spain, Sweden, Switzerland and the United Kingdom. Romania is a Candidate for Accession. Serbia is an Associate Member in the pre-stage to Membership. India, Japan, the Russian Federation, the United States of America, Turkey, the European Commission and UNESCO have Observer Status.

- The UK Science and Technology Facilities Council [www.stfc.ac.uk] coordinates and manages the UK’s involvement and subscription with CERN.

- The University of Warwick researchers who led this work are funded by the Science and Technology Facilities Council and the European Research Council.

- Further information on these results can be found in the LHCb collaboration public web page (http://lhcb-public.web.cern.ch/lhcb-public/Welcome.html#TwoSt) and the CERN Courier Sept. 2014 edition (http://cerncourier.com/cws/article/cern/58193)

Source: Warwick University