From CERN: “CMS and LHCb to present rare B-sub-s particle decay”

CERN New Masthead

19 July 2013
Cian O’Luanaigh

“New results to be presented today at the European Physical Society’s High Energy Physics conference (EPS-HEP 2013) in Stockholm, Sweden, have put the Standard Model of particle physics to one of its most stringent tests to date. The CMS and LHCb experiments at CERN’s Large Hadron Collider (LHC) will present measurements of one of the rarest measureable processes in physics: the decay of a Bs (pronounced B-sub-s) particle into two muons.

Standard model with Higgs New
Standard Model

The new measurements show that only a handful of Bs particles per billion decay into pairs of muons. Because the process is so rare, it is an extremely sensitive probe for new physics beyond the Standard Model. Any divergence from the Standard Model prediction would be a clear sign of something new.

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Protons collide in the CMS detector, producing a Bs particle that decays into two muons (red lines) in this event display from 2012 (Image: CMS)

Both experiments will present results to a very high level of statistical significance (over 4 sigma for each experiment). These results are in good agreement with the Standard Model.

‘This is a great result for LHCb,’ says LHCb spokesperson Pierluigi Campana. ‘It’s precisely for measurements like this that LHCb was built. This result shows that we’re really putting the Standard Model to the most stringent test yet at LHC energies, and so far it’s coming through with flying colours.’

‘This is a process that particle physicists have been trying to find for 25 years,’ says CMS spokesperson Joe Incandela. ‘It demonstrates the incredible capability of the LHC and experiments like CMS that are able to detect such a rare process involving a particle with a mass that is roughly 1000 times smaller than the masses of the heaviest particles we are searching for now.’”

See the full article, with links, here.

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THE FOUR MAJOR PROJECT COLLABORATIONS

ATLAS
CERN ATLAS New
ALICE
CERN ALICE New

CMS
CERN CMS New

LHCb
CERN LHCb New

LHC

CERN LHC New

LHC particles

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From Symmetry: “LHCb studies particle tipping the matter-antimatter scales”

March 12, 2013
Kelly Izlar

The LHCb experiment at CERN reports precise new measurements—but leaves open the question of why our matter-dominated universe exists.

lhcb
LHCb

“Today, scientists from CERN’s LHCb experiment announced new results in the study of the evolution of our matter-dominated universe.

The face-off between matter and antimatter was supposed to be a fair fight. The big bang should have created equal quantities of matter and antimatter, which are identical to one another but with some opposite properties such as charge. As matter and antimatter interacted over the past 13 billion or so years, they should have annihilated each other, stripping our young universe of its potential and leaving it a void.

But scientists think something happened in those first moments to upset the balance, skewing the advantage slightly toward matter.

Over the past several decades, scientists have found that some particles decay into matter slightly more often than they decay into antimatter. The Standard Model of particle physics predicts a certain amount of this imbalance, called charge parity [CP] violation.

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The Standard Model of elementary particles, with the three generations of matter, gauge bosons in the fourth column and the Higgs boson in the fifth.

However, the points this wins for matter can’t account for the amount of it left over in our universe. In fact, calculations suggest that it’s not enough for even a single galaxy. Since there may be as many as 500 billion galaxies in our universe, something is missing.

‘We think there has to be another source of CP violation that you don’t see in the Standard Model,’ says Sheldon Stone, group leader of Elementary Particle Physics at Syracuse University and a member of LHCb. ‘The source of this CP violation can be new forces carried by new particles, or even extra dimensions.’

Physicists are looking beyond the Standard Model for another source of CP violation that gave rise to galaxies, stars, planets and, eventually, us.

In 2011, LHCb analysis hinted that the CP violation in D mesons went beyond the amount predicted in the Standard Model, a possible sign of new physics in the works.

But in results presented today at the Rencontres de Moriond physics conference in Italy, those hints of new physics have melted away, reinforcing the predictions in the Standard Model of particle physics and leaving us with the mystery of why our universe is made of so much matter.

‘If we look at it as the glass being half empty, we could be disappointed that the hint for something exciting isn’t confirmed,’ says Tim Gershon, LHCb physics coordinator and professor at the University of Warwick. ‘On the other hand, there was a lot of theoretical work suggesting models to explain effects we’ve seen. New results constrain the models and tell us something about nature.'”

See the full article here.

Symmetry is a joint Fermilab/SLAC publication.


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From BBC: “The Hunt for the Higgs: A Horizon Special”

I was hunting around the BBC looking for something else when I came upon an excellent video originally broadcast in January 2012. While it is one year old, and while the question of the Higgs boson is probably very close to being answered*, still this video presents a valuable lesson.

Our host is Prof JIM AL-KHALILI, OBE, Professor of Theoretical Physics and Chair in the Public Engagement in Science at the University of Surrey.

JA
Prof Jim Al-Khalili

The video is especially valuable because it ventures into the LHCb Collaboration at CERN’s incredible LHC.

lhcb

In this section on the LHCb experiment, the subjects of Broken Symmetry and the theory, to date untested, of Supersymmetry are explored. These subjects were not at all present in the PBS Frontline piece The Atom Smashers (2008), nor the BBC video The Big Bang Machine(2008).

If you use either the Opera browser or Firefox, there are excellent video download utilities for saving an .mp4 in at least 720p HD.

I hope that you will enjoy the video and might add it to your collection.

The BBC page for the video is here.

*On July 4, 2012 The General Director of CERN, Rolf-Dieter Heuer, announced that both the ATLAS and CMS collaborations had discovered a new particle with a degree of certainty [beyond five Σ (sigma)] which placed the find beyond doubt. The particle was a boson. But, there was not then and there is still not now certainty that the find was the Higgs boson. That has yet to be confirmed. This confirmation might wait until the completion of the International Linear Collider.

#atlas, #basic-research, #bbc, #cern, #lhc, #lhcb

From Symmetry: “Scientists already planning for LHC long shutdown”

September 10, 2012 Re-posted 12.17.12 by Symmetry
Signe Brewster

Next year, scientific collaborations will take full advantage of the Large Hadron Collider’s time without beam.

“The Large Hadron Collider will go into a long shutdown early next year to allow scientists and technicians to prepare it for higher collision energy in 2015. It has been running at 7 TeV; scientists plan for it to reemerge at upward of 13 TeV. Beginning in February of 2013, highly coordinated teams will spend 20 months preparing its equipment for the change. Higher luminosity means more particle collisions, and the experiments will need more advanced equipment to keep up. With the detectors the most accessible they have been since their original construction, the four big LHC experiments will take the opportunity to perform upgrades and routine repairs. The collaborations already have plans for the new year.

man at cern

ALICE
Alice Icon New
The ALICE experiment focuses on collisions of heavy ions to study the conditions present just after the big bang. The collisions produce a quark-gluon plasma, a hot soup in which quarks travel freely instead of being bound into particles. They also produce high-energy quarks and gluons that interact with the plasma and then fragment into jets of particles and gamma rays.

ALICE will install a new part to a system that records the energy of particles. The new Di-Jet Calorimeter will broaden the experiment’s ability to measure the energy of individual gamma rays. Scientists can study an individual gamma ray to infer the energy of the quark from which it was emitted. That way, they can study how the quark-gluon plasma affects the energy of the quark and resulting jet of particles.

ATLAS
AtlasExperiment

ATLAS will add a fourth layer of pixels, known as the Insertable B-Layer, to its pixel detector. The increased number of pixels will enable measurements at a location closer to where particle collisions occur and allow scientists more accurately to identify jets of particles produced from bottom quarks.

Identifying these particles is important in the search for the Higgs boson, which, according to the Standard Model, frequently decays into bottom quarks. The ATLAS and CMS experiments discovered a Higgs-like particle this summer.

CMS

CMS Logo

The LHC experiments cannot record data from every single collision that occurs, so they select or discard this information at a split second’s notice using automatic triggers. At higher luminosity, the experiments will deal with more collisions and therefore will need better trigger systems.

During the long shutdown, the CMS experiment plans to add a new layer to their muon detector, which will help them to decide which collisions are worth studying.

LHCb

LHCB Icon

LHCb’s most important project during the shutdown will be to replace a segment of beam pipe and its support structures. The new pipe will be able to withstand temperature changes and radiation better, and the lighter support structure will reduce background in the detector.

LHCb will also begin to prepare for the next planned shutdown, in 2018, when they will install an upgrade to their detector.

See the full article here.

Symmetry is a joint Fermilab/SLAC publication.

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From CERN Blog at Quantum Diaries: “How is new physics discovered?”

IT HAS BEEN A WHILE SINCE I HAVE BEEN ABLE TO PRESENT A POST FROM QUANTUM DIARIES. MY AUDIENCE IS A MORE GENERALIST PUBLIC – INTERESTED, EDUCATED, BUT NOT PROFESSIONAL SCIENTISTS. NOW COMES A POST WHICH I BELIEVE MIGHT BE APPROACHABLE FOR MY READERS.

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Pauline Gagnon

2012.09.28
Pauline Gagnon

“Finding an experimental anomaly is a great way to open the door to a new theory. It is such a good trick that many of us physicists are bending over backward trying to uncover the smallest deviation from what the current theory, the Standard Model of particle physics, predicts.

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Standard Model

This is the approach the LHCb collaboration at CERN is pursuing when looking at very rare decays. A minute deviation can be more easily spotted for rare processes. One good place to look is in the rate of K meson decays, a particle made of one strange quark s and one anti-down quark d.

Recently, the LHCb collaboration has turned its attention to measuring the decay rate of the short-lived kaons K0S, the only K mesons decaying fast enough to be seen with precision in their detector.”

I hope that is enough to entice you to read further.

LHCB
LHCb Collaboration

Pauline Gagnon is a very good writer. Read and enjoy the rest of her post here. While you are at it, look around at the various Quantum Diary blogs, Twitter feeds,member organization web sites.

Participants in Quantum Diaries:

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Triumf

US/LHC Blog

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From CERN: “The LHC and its successors”

Anaïs Schaeffer
2012-03-12

“In one year, the LHC will begin to change. During the first long shutdown, from December 2012 to late 2014, the machine will go through a first phase of major upgrades, with the objective of running at 7 TeV per beam at the beginning of 2015.

With this long technical stop and the two others that will follow (in 2018 and 2022), a new project will see the light of day. Current plans include the study of something that looks more like a new machine rather than a simple upgrade: the High Luminosity LHC (HL-LHC). Much more powerful than the current machine, the HL-LHC will aim for a very high production rate of events for the ALICE, ATLAS, LHCb and CMS detectors. ‘On the machine side, the HL-LHC project has been approved and should be co-funded as a study by the EU,’ says Oliver Bruning, Leader of the Accelerators and Beam Physics Group (ABP) of BE Department HL-LHC Deputy Project Leader and Accelerator Study Leader of LHeC. ‘On the experiments’ side, teams are now working on the technical design reports. This part has not been approved yet, and the funds are still to be found.’ If everything goes well, the HL-LHC could be ready to start running in around 2020.

In the meantime, engineers and physicists have begun to work on another project, which could be built in parallel to the HL-LHC. Called LHeC, it will be designed for collisions between electrons and protons. ‘The LHeC could be implemented in two different ways,’ explains Frank Zimmermann, member of the BE/ABP Group and Deputy EuCARD Coordinator. ‘The first one would be to build an electron ring in the LHC tunnel, on the top of the current one – leading to what physicists call a ring-ring machine. The second solution would be to build a separate tunnel of about 9 km that would host two superconducting LINACs in a racetrack Energy Recovery LINAC (ERL) configuration where the two LINACs are connected via return arc. The electron beam would be accelerated in three passages through each LINAC, before electron-proton collisions would occur at the highest energy in the LHC.’ In both cases, the electron and proton beams would cross at a unique point, where a new experiment would need to be installed.”

Excited? See the full article here.

Meet CERN in a variety of places:

Cern Courier

ATLAS

i2

ALICE

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LHCb
i4

LHC


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From Pauline Gagnon at CERN Via Quantum Diaries: “Charm and beauty: LHCb has it all!”

Pauline Gagnon
November 18, 2011

“This week, the LHCb experiment reported an anomaly they have just observed in the decays of charmed mesons. Could this be the tip of the iceberg for new physics?

As I reported before, the main goal of the LHCb experiment is to use heavy quarks (called beauty and charm quarks) to make precise measurements in the hope of detecting small deviations from the Standard Model, the theoretical framework that has been guiding particle physicists for a few decades. But it has a few known shortcomings that make us think new physics should be discovered soon.

This is a great model that allows theorists to make very accurate predictions. So far, every single one of them has proven to be true but if we were to find a flaw, it would be like discovering the secret passage guiding us further into our investigation of how matter works.

The results presented this week by the LHCb experiment hint in this direction, although as usual, further checks are needed.”

See the full article, very informative, here.

Participants in Quantum Diaries:

Fermilab

Triumf

US/LHC Blog


CERN

Brookhaven Lab

KEK

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