LHCb experiment: Difference between revisions

Revision as of 01:42, 19 July 2013

Revision as of 11:32, 19 September 2013

Line 5:

== Physics goals ==

The experiment has wide physics program covering many important aspects of Heavy Flavor (both beauty and charm), Electroweak and [[Quantum chromodynamics|QCD]] physics. Six key measurements have been identified involving B mesons. These are described in a roadmap document <ref>[http://arxiv.org/abs/0912.4179], Roadmap for selected key measurements of LHCb</ref> that form the core physics programme for the first high energy LHC running in 2010–2012. They include:

* Measuring an upper limit on the branching ratio of the rare B_s → μ⁺ μ⁻ decay.

* Measuring the forward-backward asymmetry of the muon pair in the [[Flavor changing neutral current|flavour changing neutral current]] B_d → K^* μ⁺ μ⁻ decay. Such a flavour changing neutral current cannot occur at tree-level in the [[Standard Model]] of Particle Physics, and only occurs through box and loop Feynman diagrams; properties of the decay can be strongly modified by new Physics.

* Measuring the [[CP violation|CP violating]] phase in the decay B_s → J/ψ φ, caused by interference between the decays with and without [[B–Bbar oscillation|B_s oscillations]]. This phase is one of the CP observables with the smallest theoretical uncertainty in the [[Standard Model]], and can be significantly modified by new Physics.

Line 13:

== The LHCb detector ==

The fact that the two b-hadrons are predominantly produced in the same forward cone is exploited in the layout of the LHCb detector. The LHCb detector is a single arm forward spectrometer with a polar angular coverage from 10 to 300 [[radian|milliradians (mrad)]] in the horizontal and 250 mrad in the vertical plane. The [[asymmetry]] between the horizontal and vertical plane is determined by a large [[dipole magnet]] with the main field component in the vertical direction.

[[Image:Lhcbview.jpg|700px|LHCb detector among the bending plane]]

Line 26:

=== Main Tracker ===

The main tracking system is placed before and after the dipole magnet. It is used to [[event reconstruction|reconstruct]] the trajectories of [[electric charge|charged]] particles and to measure their momenta. The tracker consists of three subdetectors:

* The Tracker Turicensis, a silicon strip detector located before the LHCb dipole magnet

* The Outer Tracker. A straw-tube based detector located after the dipole magnet covering the outer part of the detector acceptance

acceptance

* The Inner Tracker, silicon strip based detector located after the dipole magnet covering the inner part of the detector acceptance

Line 37 ⟶ 36:

=== ECAL ===

The [[Electromagnetism|electromagnetic]] and [[hadron]]ic [[calorimeter#High-energy particle calorimeter|calorimeters]] provide measurementmeasurements of the [[energy]] of [[electrons]], [[photons]], and [[hadrons]]. These measurements are used at [[trigger (particle physics)|trigger level]] to identify the particles with large transverse momentum (high-Pt particles).

=== Muon System ===

Line 46 ⟶ 45:

During the 2011 proton-proton run LHCb recorded a luminosity of 1 fb⁻¹

<ref>[http://lpc.web.cern.ch/lpc/lumiplots_2011.htm], 2011 LHC Luminosity Plots</ref> at

a center-of-mass energy of 7 TeV. In 2012 about 2 fb⁻¹ was collected at 8 TeV.<ref>[http://lpc.web.cern.ch/lpc/lumiplots_2012.htm], 2012 LHC Luminosity Plots</ref> These datasets allow to carry out the baseline physics program of the experiment of precision Standard Model tests andtogether with many additional measurements. The analysis led to evidence for the [[Flavor-changing neutral current|flavour changing neutral current]] decay B_s → μ μ.<ref>[http://arxiv.org/abs/1211.2674], Arxiv: First evidence for the decay Bs → μ+ μ-</ref> The latterThis measurement impacts the parameter space of Supersymmetry[[supersymmetry]].

==See also==