111/29/2010

Emrah Tiras, University of Iowa

SELEX(SEGMENTED LARGE-X BARYON

SPECTROMETER)

Fermilab 96-97

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OutlineSELEX E781Physical Goals of SELEX SELEX Collaboration SELEX Experimental SetupDetector OverviewSpectrometers Conclusion

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SELEX is a fixed target experiment at Fermilab which

took data during the year 96-97 with 600 GeV Σ−, π−

during two years of running it recorded 15.2 billion hadronic interaction events.

is a multistage charged particle spectrometer with high acceptance of Feynman X- Parameter.

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Physical goals of the SELEX The study of;

the lifetime of weakly decaying charmed baryons.

the charmed baryon production in the 600 GeV hyperons' beam.

the excited baryons. the charm baryon semileptonic decay. charm baryon spectroscopy both charm and non-charm physics.

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SELEX Experiment Collaboration

125 participants from 20 institution in 11 countries (USA, Russia, Turkey, Brazil, China, Germany, Israel, Mexico, UK and Italy)

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The SELEX Experiment Setupis consisted of;

a beam linea target areaa multistage spectrometer

The SELEX experiment used the Fermilab charged Hyperon beam which is composed of 50% Σ⁻ and 50% π⁻ with the energy of about 600 GeV for negative polarity; and 92% p and 8% π⁺ with the energy of 540 GeV for positive polarity.

The beam was run at the forward production angle(Θ=0˚)

The experiment was designed to have high acceptance and resolution in Xf region 0.1<Xf<1.

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Schematic view of SELEX spectrometers

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M3 magnetM2 MagnetM1 Magnet

Z

M1 spectrometer

M2 spectrometer

M3 spectrometer

X

Vertex Spectrometer

Beam Spectrometer

Beam

Hyperon Magnet

Targets

Exit

The beam spectrometer is between the exits of the hyperon magnet and target region. The vertex spectrometer is between the targets and M1 spectrometer. The M1,M2,M3 spectrometers are located after the corresponding analyzing magnets.

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SELEX Detector Layout

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Detector Overview 1(The SELEX Exp. had an extensive particle identification system)

Vertex Silicon Strip Detector (SSD): The heart of the experiment with 4 µm transverse position resolution at 600 GeV.

Beam Transition Radiation Detector(TRD): Beam particles (Σ⁻/π⁻, p/π⁺) were tagged

3000 phototube Ring Imaging Cherenkov Counter (RICH): identify the secondary particles: electrons, muons, pions, kaons, protons, and even hyperons.

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The Electron Transition Radiation Detector (ETRD): to separate electrons from hadrons which is important for the semileptonic decay physics.

Three lead glass detectors: to identify and measure the energy of the photons and electrons.

SELEX also has a precise tracking system and 3 analyzing magnets to measure particle momentum.

11/29/2010 Emrah Tiras, University of Iowa

Detector Overview 2

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Analyzing magnets SELEX apparatus has 3 analyzing magnets

that were used to measure track momentum.

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Name Z[cm]

Aperture[cm]*[cm

]

B[kG]

Pt[GeV]

M1 190 61*51 11.98 0.73

M2 745 61*25 14.66 0.84

M3 4240 61*51 6.85 0.42

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SPECTROMETERSThe SELEX experiment was composed of five

stage spectrometerBeam Vertex M1M2M3

Each spectrometer other than Vertex which is designed to create high resolution tracking near target, contained a bending magnet.

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Beam Spectrometer is consisted of;

the hyperon production target the hyperon magnet the beam particle identification

detectors beam tracking detectors and scintillators

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M1 Spectrometeris made up of;

a magnet with 1.3 T magnetic field which gives a transverse momentum.

2 large area silicon micro-strip detectors (LASD) measure the beam and primary and secondary vertex

tracks. proportional wire chambers (PWC)

measure the momenta of the tracks. drift chambers (DC)a photon calorimeter (Lead Glass

Electromagnetic Calorimeter)

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M1 Spectrometerwas designed to analyze the particles from

2.5 to 15 GeV/c momentum range.Low energy particles(from the vertex region)

are tagged and photon energies are measured at this stage.

This plays a crucial role in measuring the momentum of upstream trucks.

This was built here (University of Iowa)

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M2 Spectrometer is consisted of;

a magnet with 1.5 T magnetic field.LASDs7 PWCs with 2 mm wire spacing 6 Vector Drift Chambers (explanation on the next slide)2 hodoscopes6 Electron Transition Radiation Detector(ETRD)

were designed to give good electron identification. Ring Imaging Cherenkov (RICH) detector.

Provides the particle identification information for the hyperons' daughter particles.

is designed to identify particles with momentum higher than 15 GeV/c

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M3 Spectrometer is consisted of;

a magnet with 1.3 T. 2 Multiwire Proportional Chambers(PWC)3 Vector Drift Chambers;

Were designed to provide the short track segments of downstream decay products, charged particles as well as the position information.

a photon Calorimetera neutron Calorimeter

was built jointly by the University of Iowa and the Trieste groups.

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Vertex Spectrometerstarts at the downstream end of the last target and ends

at the middle of the M1 spectrometer. is consisted of 20 Vertex Silicon Detectors(SSDs)

mounted to five station, four SSDs at each.the first 8 detectors, called 5 cm-detectors, have 20 µm

pitch and 5.1*5.0 cm² active area.The downstream 12 detectors, called mosaic detectors,

have 25µm pitch and 8.3*3.2 cm² active area. Each of the detectors has greater than 98% hit

detection efficiency and spatial resolution about 6.5 µm.

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First time the doubly charmed baryon Ξcc⁺ was interpreted from the experiment: Ξcc⁺ Λc⁺K⁻π⁺

In 2002, the SELEX collaboration published evidence of a doubly charmed baryon Xi (Ξcc), containing two charm quarks.

They figured out a new particle decaying in two modes:DsJ ⁺ D˚KDsJ ⁺ Dsη

New measurements for D˚ and D⁺ lifetimesτ₁: (409.6±1.1±1.5)fs τ₂: (1039.4±4.3±7.0)fs

Precision measurements of the Ξc⁺ and D˚ and Ds lifetimes.Production asymmetry of Ds from 600 GeV/s Σ and π beam.At that time all these new experimental data had good

agreement with theory.

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Conclusion

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Additional42 graduate students in Physics completed their

thesis with this experiment(data) from 1997-2010.8 graduate students from here. http://www-selex.fnal.gov/documentation/thesis

Some useful articles about the experiment.Precision measurements of the [Lambda]c⁺ and D˚

lifetimes Phys. Rev. Let. 86, 5243 (2001).Measurement of the Ds lifetime Physics Letters B

523 (2001), 22-28.Production Asymmetry of Ds from 600 GeV/c Sigma⁻

and pi⁻ beam Physics Letters B 558 (2003), 34-40.

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References Akgun, U.: CMS HF Calorimeter PMTs and Ξc

+ Lifetime Measurement (University of Iowa, 2003)

Ayan, A.S.: The CMS Forward Calorimeter Prototype Design Studies and Ωc

0 Search at E781 Experiment at Fermilab ( University of Iowa, 2004)

Fermi National Accelerator Laboratory [Internet]. 2003. Chicago: Fermi National Accelerator Laboratory SELEX Collaboration; 2003 [cited 2003 Aug 8]. Available from: http://www-selex.fnal.gov

High Energy Physics Division (HEPD) of Petersburg Nuclear Physics Institute (PNPI) of Russian Academy of Sciences [Internet]. 2010. Russia: High Energy Physics Division; 2010 [cited 2010 Nov 1]. Available from: http://dbserv.pnpi.spb.ru/hepd/activities/hep.html

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Thank you for

listening to my presentation…

Emrah Tiras

11/29/2010 Emrah Tiras, University of Iowa