LHCb – Large Hadron Collider beauty experiment

LHCb is an experiment set up to explore what happened after the Big Bang that allowed matter to survive and build the Universe we inhabit today

Fourteen billion years ago, the Universe began with a bang. Crammed within an infinitely small space, energy coalesced to

form equal quantities of matter and antimatter. But as the Universe cooled and expanded, its composition changed. Just one second after the Big Bang, antimatter had all but disappeared, leaving matter to form everything that we see around us — from the stars and galaxies, to the Earth and all life that it supports.

6 September 2010: Beautiful atoms

The LHCb has observed beautiful atoms. The atoms are bound states of the beauty quark and anti-beauty quark. The atoms are bound by the strong force, the force which also binds quarks inside proton. The beautiful atom is 10 times heavier than the proton (yes, we can create mass from energy using famous Einstein formulae E=mc2), has a size sligtly smaller than the size of the proton but about 100 000 times smaller than the size of the hydrogen atom which is composed of a proton and an electron and is bound by the electromagnetic force. Just like ordinary atoms beauty and anti-beauty quarks form different quantum states with different angular momenta and different spin orientations (see figure below right). Only the states marked 1S, 2S and 3S are observed at LHCb by detecting their decay into a μ+ and μ pair (left).

The figures above show the invariant mass of μ+ and μ particles (left) and the schematic view of the beautifull atom quantum states (right), click in images to get them in higher resolution.

The beauty-anti-beauty atom, called “Upsilon” was discovered in 1977 at the proton-antiproton collider at Fermilab near Chicago.

The states 1S, 2S and 3S do not decay into Beauty Particles since their mass is lower than the sum of masses of Beauty and anti-Beauty particles (BB threshold in the figure). On the other hand the state 4S does decay. This feature is used by the experiments BABAR and BELLE producing the 4S state at e+e colliders as a source of Beauty and anti-Beauty particles.

The charm and anti_charm quarks form two bound atom states 1S and 2S called J/psi and psi’ observed at LHCb through their decay into a μ+ and μ pair (left) and a e+ and e pair (right).

click in images to get them in higher resolution.

———————————————————————————————————–

left). The figures above show the invariant mass of μ+ and μ particles (left) and the schematic view of the beautifull atom quantum states (right), click in images to get them in higher resolution.

The beauty-anti-beauty atom, called “Upsilon” was discovered in 1977 at the proton-antiproton collider at Fermilab near Chicago.

The states 1S, 2S and 3S do not decay into Beauty Particles since their mass is lower than the sum of masses of Beauty and anti-Beauty particles (BB threshold in the figure). On the other hand the state 4S does decay. This feature is used by the experiments BABAR and BELLE producing the 4S state at e+e colliders as a source of Beauty and anti-Beauty particles.

The charm and anti_charm quarks form two bound atom states 1S and 2S called J/psi and psi’ observed at LHCb through their decay into a μ+ and μ pair (left) and a e+ and e pair (right).

click in images to get them in higher resolution.

22 July 2010: From a B to Z, LHCb explores the particle alphabet

LHCb has unveiled pictures of a Z boson inside the experiment. This boson is one of the best understood of all particle species. It shows us how the forces of electricity, magnetism and radiation are connected inside the Standard Model, our theory of particle physics. Measurements of how often we see Z bosons inside LHCb will provide a sensitive test of how well our theory describes this particle at the record breaking energies of the LHC.

click in images to get them in higher resolution

In this picture the Z boson has decayed immediately to two muons μ, shown by the thick white lines which point to the green muon chamber hits in the outer circle of the Eolas display (described in 10 June 2010 News). Not much else happens inside LHCb when a Z is at work – only a few other particles are visible – and this makes it an easy particle to find. We’re looking forward to collecting more of them now, and really testing how well the Standard Model performs for us.

———————————————————————————————————–

12 July 2010: LHCb is younger!

The average age of the LHCb Collaboration members has strongly decreased after arrival of the LHCb summer students seen below in front of the Globe of Science and Innovation. The Summer Students follow the lectures given at the first floor of the Globe in the morning. During the breaks they can visit the new CERN exhibition “Universe of Particles” located on the ground floor and the rest of the time they make an important contribution to the LHCb data taking and data analysis.

click in image to get it in higher resolution

———————————————————————————————————–

10 June 2010: The W boson in action

LHCb has taken its first snapshots of the W boson in action. This particle conveys the weak force, which makes certain forms of radioactivity possible. It is shown here having decayed to a muon μ (shown as a straight white line, pointing to the filled green muon detector hit circles in the 2D picture, and as a red line pointing to blue muon hits in the 3D picture), which we see, and a neutrino ν, which we don’t, with very little else around it.

click in images to get them in higher resolution

Eolas (gaelic for ‘knowledge’) is a 2D view of a collision inside LHCb. It is a transmogrified view, chosen to illustrate where particles deposit energy as they fly outwards from the collision point. The radius represents flight through the detector along the beam direction – through the tracking detectors, then the first muon chamber, then the electromagnetic and hadronic calorimeters, and finally the last four muon chambers. The φ angle represents the angle in the x,y direction perpendicular to the beam. Information is colour coded. Particle tracks are shown by the dashed lines. The transverse momentum of the particle is shown by the solid white long along this path – the higher this is, the longer the solid white bar is. Yellow bars show energy deposited in the electromagnetic calorimeter, cyan energy deposited in the hadronic calorimeter. Deposits in muon chambers are illustrated by green circles. If these are filled, they are associated with a particle track passing through them.

We will use samples of W bosons to test our theory of particle physics, the Standard Model, to high precision. This is exciting because we don’t know yet if our theory holds at LHC energies – if it doesn’t, if there are new particles to find in nature, we’ll see W bosons behaving in a way we don’t expect. With these first snapshots taken, we’re on our way to finding out.

The W boson was discovered in 1983 at CERN by the UA1 and UA2 experiments giving the Nobel Prize to Carlo Rubbia and Simon van der Meer.

———————————————————————————————————–

7 May 2010: Strange Beauty and Charm

LHCb has reconstructed an event having all characteristics of a Strange Beauty Particle decay! A computer view of this event is shown below. The Strange Beauty Particle (called Bs) is composed of a quark b (b is for beauty) and an anti-quark s (s is for strange). It is produced by the collision of two 3.5 TeV protons from the LHC at a location marked as “PV” (Primary Vertex), together with many other particles (not shown). The Bs decays after travelling about 1.5 mm into three particles called μ, Ds+ and neutrino ν at a place marked “SV” (Secondary Vertex). The ν is not detected since it can even traverse the whole Earth without any interaction. The Charm Particle Ds+ is composed of a c quark (c is for charm) and anti-quark s. The Ds+ particle decays in turn after travelling 6.5 mm into three long lived particles K+, K and π+ in a place called “TV” (Tertiary Vertex). The K+, K and π+ are traversing the LHCb detector where the tracking system is used to reconstruct their trajectories with such a very high precision that it is clear that the particles come from three different places called vertices.

click in image to get it in higher resolution

———————————————————————————————————–

21 April 2010: First reconstructed Beauty Particle

LHCb has reconstructed its first Beauty Particle! You can see below a computer view of this event in two projections (images on the left hand side). The Beauty Particle (called B+) is composed of an anti-quark b (that has a very short lifetime of 1.5 thousandth of a nanosecond!) and a quark u. It is produced by the collision of two very high energy protons from the LHC at a location marked as “Primary vertex”, together with many other particles (shown in black). The B+ decays after travelling about 2mm into two particles (called J/ψ and K+) at a place marked “B decay vertex”. The J/ψ particle decays in turn immediately into two long lived particles called μ+ and μ. The μ+ , μ and K+ are traversing the LHCb detector where the tracking system is used to reconstruct their trajectories with such a very high precision, that it is clear they do not come from the primary vertex. The fact that the reconstructed tracks do not cross exactly in two points reflects experimental precision of computer reconstruction. The real particle tracks originate at the two vertices. The images on the right hand side show the same event when the tracks from the “Primary vertex” are forced to come from the “Primary vertex”.

click in images to get them in higher resolution

The LHCb physicists have collected about 10 million proton-proton collisions in order to find this first Beauty Particle. The reconstruction of each event is not easy, there are about 100 particle tracks reconstructed in this event, see full event display below.

More details: LHCb physicists have calculated invariant mass of μ+ and μ particles from the “B decay vertex” and found that it correspond to the J/ψ mass, see below invariant mass distribution of all μ+ and μ pairs with the peak corresponding to the J/ψ decays. The reconstructed invariant mass of J/ψ and K+ is 5.32 GeV, in agreement with to the known B+ mass, 5.5 times higher than the colliding proton mass but 650 times smaller than the colliding proton energy (yes, we can create mass from energy using famous Einstein formulae E=mc2).

see comments in articles: NewScientist internet, magazine and ZDNet.

First

30.3.2010

Both proton beams made a full turn of LHC on Feb. 28th. A new period of great measurements with LHCb has started again and will continue for 18-24 months. On March 18th both beams have been accelerated to 3.5 TeV,

3.5×3.5 TeV

30.3.2010

see TV footage with preparation for collisions and photo above taken just after the first collisions at 12:59 on March 30 (click on picture to get it in higher resolution).

more pictures can be found here, here, and here.

proton-proton collisions

30.3.2010

Our first 3.5×3.5 TeV collision; other events can be found here.

Read CERN Bulletin article in English and French and also CERN Courier article.

see LHCb video on YouTube, and CDS as well as interview with Tara Shears.

International

8.3.2010

On March 8th, during during International Women’s Day, many many women have been present in the LHCb control roon, …

Women’s

8.3.2010

see the photos taken at the LHCb control room (click in pictures to it in higher resolution, click here to get other photos), the video interview with Monica Pepe-Altarelli here, …

Day

8.3.2010

the LHCb women poster (click in image to get higher resolution), and the CERN and the Fermilab Web pages.

2009 News

Below you may find interesting computer reconstructed events observed with the LHCb detector during the LHC restart period in November and December 2009. Click on picture to see it in higher resolution version.

Protons have ended to circulate at LHC on December 16th.

1.2 TeV collisions at LHCb

14.12.09

On December 14th 1.2 TeV proton beams have collided at LHCb during LHC machine studies. Many LHCb subdetectors, except for sensitive silicon detectors, recorded the world’s highest energy pp collisions. Other events can be found here.

proton interactions with gas

12.12.09

Position of proton interactions inside the vertex detector with residual gas are shown in blue or red, proton-proton interactions in green (more details).

K0 reconstruction

12.12.09

So called “strange particles” are produced in the proton-proton collisions and decay inside LHCb detector into two other particles reconstructed as red tracks (more details).

High multiplicity events

12.12.09

A high multiplicity event with three muon tracks (green) recorded on December 12th. Other events can be found here.

More proton-proton collisions

8.12.09

On December 8th many long tracks were reconstructed using the detectors along the whole length of the LHCb. Collision vertex is clearly observed (bottom left). The tracks are curved in the magnetic field allowing measurement of the track momentum (top left). Other events can be found here.

More proton-proton collisions

6.12.09

On December 6th protons have again collided at LHCb. Few modules of sensitive LHCb Vertex Locator VELO recorded tracks clearly indicating proton-proton collision vertex location (see picture left bottom). Other reconstructed events can be found here.

RICH rings

6.12.09

LHCb RICH detectors are used to identify particles. The circles show possible position of measured points for different kinds of particles traversing the detector. The measured points clearly choose one possibility for every circle and in this way allow to identify particles.

First proton-proton collisions

23.11.09

A proton-proton collision candidate event. On November 23 protons from two beams circulated at LHC and have collided at LHCb.

LHC news video youTube

First proton-proton collisions

23.11.09

LHCb control room at this historical moment.

LHCb November 23 pp collision video youTube, CDS

First proton-proton collisions

23.11.09

Tracks originate from the expected region inside LHCb Vertex Locator detector VELO.

First proton-proton collisions

23.11.09

Another proton-proton collision candidate event.

Annimation

23.11.09

Animation (click on picture): pp collisions and proton beam gas collisions recorded on Nov. 23, 2009. Other reconstructed events can be found here.

First reconstructed pi0’s

23.11.09

pi0 is the short lived particle decaying into two photons which were measured in the electromagnetic calorimeter ECAL. The plot above shows the nearly perfectly reconstructed pi0 mass.

First proton interactions

22.11.09

… reconstructed Vertex Locator VELO track. Other reconstructed events can be found here.

First proton interactions

22.11.09

… event reconstructed later (offline reconstruction). Particularly interesting is the blue track recorded in the Vertex Locator VELO and in the tracking chambers after the magnet.

First proton interactions

21.11.09

… not yet proton-proton interaction but interactions of the protons with residual gas inside LHC ring. Tracks reconstructed during data taking.

A splash from the LHC beam

21.11.09

LHC has restarted on November 21st. Two LHC beams have made a full turn of the LHC. Afterwards, after synchronization with the LHC accelerating system (RF capture in technical language), the beams made few hundred turns. During LHC operation LHCb has recoded splash events. The movie (click on picture) shows what LHCb detector has recorded every 25ns (1/(40 000 000) s) for a particular splash event; see individual events here.

LHCb – Large Hadron Collider beauty experiment.

Tagged on:

Leave a Reply