Tag Archives: Atlas

Determinan una propiedad de la materia tras el Big Bang

Una colaboración internacional donde participan físicos de la Universidade de Santiago de Compostela ha publicado recientemente en Physical Review C la medición más precisa hasta la fecha de una propiedad clave del plasma de quarks y gluones, el estado de la materia que dominó el Universo justo después del Big Bang. Este resultado revela la estructura microscópica de este fluido, un “líquido perfecto” desde el punto de vista de su comportamiento físico. Los resultados se obtuvieron mediante el análisis de datos de las colisiones entre núcleos pesados obtenidos en el Gran Colisionador de Hadrones (LHC) del CERN y el Relativistic Heavy-ion Collider (RHIC) en el Laboratorio de Brookhaven (EE.UU.).

ALICE-hirezf

La colaboración JET es un grupo de físicos teóricos formado principalmente por miembros de universidades de Estados Unidos donde participan varios miembros asociados, entre ellos Néstor Armesto y Carlos Salgado (Universidade de Santiago de Compostela). Su objetivo es extraer las propiedades del llamado plasma de quarks y gluones, el estado de la materia instantes después del Big Bang, cuando la temperatura y densidad eran tan altas que no permitían la formación de protones o neutrones, constituyentes del núcleo atómico.
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No Matter How Hard You Try… Standard is Standard.

The past two days of the Recontres de Moriond 2014 Electroweak conference have been very intense with many new experimental results, many insightful theoretical talks and many lively discussions. Since the topics cover neutrino experiments, astrophysical observations and Standard Model precision measurements, giving a summary is not an easy task. But I will try.

HiggsPuzzle

Fig. 1 – Is the Higgs boson the last missing piece of the Standard Model or part of a much bigger puzzle? (image courtesy of RealScience.us)

The discovery of the long-sought Higgs boson, the last missing piece of the Standard Model of particle physics, was announced in July 2012 by both the ATLAS and CMS collaborations at CERN, and the Nobel prize was awarded in October 2013 to Peter Higgs and François Englert, for proposing the mechanism responsible for breaking the electroweak symmetry and giving mass to the Z and W bosons.
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Primeras evidencias de un nuevo modo de desintegración del bosón de Higgs

La colaboración internacional delexperimento ATLASdel Gran Colisionador de Hadrones LHC acaba de hacer públicas las primeras evidencias de la desintegración del recién descubierto bosón de Higgs en dos partículas denominadas tau, pertenecientes a la familia de partículas que compone la materia que vemos en el Universo. Hasta ahora los experimentos del LHC habían detectado la partícula de Higgs mediante su desintegración en otro tipo de partículas denominadas bosones, portadoras de las fuerzas que actúan en la Naturaleza, mientras las evidencias de desintegraciones en fermiones no eran concluyentes. Esta es la primera evidencia clara de este nuevo modo de desintegración del bosón de Higgs, en cuyo análisis han participado investigadores españoles.

fig_33

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Seis incógnitas de la Física después del bosón de Higgs

El hallazgo de una partícula de tipo Higgs no es la última frontera de la Física. El LHC tiene por delante al menos veinte años de trabajo y los científicos se enfrentan a un buen puñado de incógnitas fundamentales a resolver.

¿Cuáles son éstas? ¿Qué pasos se darán ahora? En el horizonte está incluso la posibilidad de que el LHC se quede pequeño y haya que construir un nuevo colisionador.

El anuncio del hallazgo de la partícula de Higgs (o una muy parecida) no dejará a los físicos del CERN sin trabajo. Es precisamente ahora cuando se abre la etapa más fascinante de su investigación, cuando comiencen a comprobar las propiedades de la partícula que han descubierto. El LHC tiene planes hasta al menos 2025 y sus otros objetivos no son solo seguir investigando la partícula de Higgs. Además de ATLAS y CMS (los dos experimentos que anunciaron el hallazgo de un bosón a 125 GeV) existen otros cuatro detectores de partículas (LHCb, SPS, LHCf, ALICE y TOTEM) que siguen realizando pruebas.

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François Englert y Peter Higgs, Premio Nobel de Física

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Geneva, 8 October 2013. CERN physicists from ATLAS and CMS celebrated at CERN the award of the Nobel Prize in physics to François Englert and Peter W. Higgs “for the theoretical discovery of a mechanism that contributes to our understanding of the origin of mass of subatomic particles, and which recently was confirmed through the discovery of the predicted fundamental particle, by the ATLAS and CMS experiments at CERN’s Large Hadron Collider.” The announcement by the ATLAS and CMS experiments took place on 4 July 2012 at CERN. Members of the ATLAS and CMS collaborations present at CERN on Oct. 8 assembled in their building (b. 40) on the CERN Meyrin site to watch the live webcast from Stockholm. This VNR shows the physicists waiting for the announcement, celebrating the announcement and listening to a short spontaneous speech by CERN’s director general Rolf Heuer, who congratulated the theoretical physicists for the award and the experimental physicists at CERN for their discovery.
04:50.03 min / 08 October 2013 / © 2013 CERN
Director: Noemí Carabán

La Real Academia Sueca de las Ciencias ha otorgado el premio Nobel de Física 2013 al científico belga François Englert (1932) y al británico Peter W. Higgs (1929) por su “descubrimiento teórico de un mecanismo que contribuye a la comprensión del origen de la masa de las partículas subatómicas, y que recientemente se confirmó a través del descubrimiento de la partícula fundamental predicha, en los experimentos ATLAS y CMS en el Centro Europeo de Física de Partículas (CERN)”.

CERN-MOVIE-2013-118-002-posterframe-640x360-at-20-percent

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Google Street View goes underground at LHC

A virtual tour of the Large Hadron Collider and the ATLAS, CMS, LHCb and ALICE experiments is now available on Google Street View.
by Sarah Charley and Ashley WennersHerron.

 

Visitors all over the world can now explore CERN’s massive detectors and 1200 meters of the Large Hadron Collider tunnel with Google Street View—a Google product that links a series of panoramic photos into a virtual tour.

In 2011, members of Google’s Zurich team joined forces with CERN and spent two full weeks photographing the subterranean experiments and portions of the LHC, as well as the interiors of surface buildings at the laboratory. Compiling the imagery and coordinating the GPS locations took an additional two years, according to CERN photographer Max Brice.

“Every three meters, they took a six-sided panorama of the tunnel,” Brice says. “Then we had to figure out the coordinates of every image. It came out to 6000 points for us to track.”

This new view of CERN allows visitors to explore the world’s largest particle accelerator and visit the caverns that house ATLAS, CMS, LHCb and ALICE (pictured above)—experiments responsible for expanding our scientific knowledge about new particles, like the Higgs boson, and increasing our understanding of the early universe.

“I don’t think people realize how much of CERN is underground,” Brice says. “On the surface, you see our buildings, but go underground and you can really start to get an idea of the big science done here.”

The CERN team hopes that these images will help make the laboratory and its research more accessible to the general public, as well as bridge the geographic gap between CERN and researchers on other continents, who analyze data taken by CERN experiments but don’t necessarily ever visit the laboratory themselves.

“CERN is making these views available to the general public in order to share our amazing facilities with as wide an audience as possible, but they also play another role,” says James Gillies, head of communications at CERN. “With the size and geographical diversity of the collaborations, these views also allow scientists working on the experiments to explore their detectors, even if they don’t get the chance to come here in person.”

The images will also help people visiting CERN navigate the lab, which stretches between Switzerland and France.

Google and CERN continue to collaborate on this project and hope to make many more CERN facilities virtually available to the public.

Pues sí, podeis a partir de ahora, daros un tour con Google Street View por el LHC y sus experimentos ATLAS, CMS,……etc.

Solo se necesita eso si. tener una cuenta de gmail y las cuentas que google te asocia.

https://www.google.com/maps/views/streetview/cern?gl=us

Visto en http://www.symmetrymagazine.org/

Long-standing discrepancy put to rest

This morning at the European Physics Society conference in Stockholm, the LHCb experiment operating at the Large Hadron Collider (LHC) CERN brought one more argument to put to rest a long-standing discrepancy that had kept theorists puzzled for nearly two decades.

LHCb presented the most precise measurement to date of the b baryon lifetime. A baryon is a family of composite particles made of three quarks.  For example, protons and neutrons are made of a combination of u and d quarks.  What makes b baryons so special is that they contain a b quark, a much heavier type of quark. Composite particles containing b quarks like B mesons (made of a b and either a u or d quarks) and b baryons are unstable, meaning they have a short lifetime. About one picosecond after being created, they break down into smaller particles.

In theory, both B mesons and b baryons should have approximately the same lifetime. But in the 1990’s, when CERN operated with its previous accelerator called LEP (Large Electron Positron collider), all experiments measured a systematically shorter lifetime for b baryons than B mesons as can be seen on the plot below. Although the LEP experimental errors were quite large, the general trend of lower values was very puzzling since all four experiments (ALEPH, DELPHI, OPAL and L3) were working independently. Lb_lifetime_comparison

The various b baryon lifetime measurements over time from the oldest results at the bottom to the three latest results from the LHC experiments at the top. The measured value has now shifted toward a value of 1.5 picoseconds, as measured for the B mesons.

This prompted theorists to re-examine their calculations and to look for overlooked effects that could explain the difference. Despite all efforts, it was nearly impossible to reconcile the measured b baryon lifetime (somewhere between 1.1 to 1.3 picosecond) with the B meson lifetime at around 1.5 ps.

Nearly a decade later, D0 and CDF, the two experiments from another accelerator, the Tevatron near Chicago, started closing the gap. It took another decade for the LHC experiments to show that in fact, there is no large difference between b baryon and B meson lifetimes.

Already, earlier this year, ATLAS and CMS both reported values in line with the B meson lifetime. With this latest and most precise result from the LHCb experiment, there is now enough evidence to close the case on this two-decade-old discrepancy. LHCb measured the b baryon lifetime to be 1.482 ± 0.018 ± 0.012 ps. The ratio to the B meson lifetime is 0.976 ± 0.012 ± 0.006, very close to one as theoretically expected.

One possible explanation is that all LEP experiments were affected by a common but unknown systematic shift or simply, some statistical fluctuation (i.e. bad luck). The exact cause might never be found but at least, the problem is solved. This is a great achievement for theorists who can now rest assured that their calculations were right after all.

 

http://www.quantumdiaries.org

Pauline Gagnon

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