Calorimeters In Action!!

Calorimeters In Action!! ILC Calorimeter School CCAST & TUHEP, Tsinghua University Apr. 22 – 26 Jae Yu University of Texas at Arlington

Lecture Outline • Preparation of a HEP experiment • Physics Goals • Accelerators and Detectors • NuTeV Calorimeter • Physics Goals • Beam Characteristics • Detector and its performance • DØ Calorimeter • Physics Goals • Beam Chracteristics • Detector and its performance ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Preparation of a HEP Experiment • Decide on physics topics and scientific goals to accomplish • Explore accelerators, existing, upgraded or new • Define the necessary detector performance requirements to accomplish the measurements of the topics • Define the design parameters and look into available or new technologies to fit the performance parameters • Perform Monte Carlo simulations to refine the requirements and test technical feasibilities • Perform R&D for various detector technologies and construct and test prototypes • Design an integrated detector and test them in the beam to understand, improve and calibrate its performance • Construction, commissioning, data taking and analysis ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Design Considerations – Scientific Goals • What are the critical physics questions to answer? • Always changing, a moving target • Theoretical predictions based on previous theories and the results of experimental tests • Previous experimental results • Did we measure certain quantities to a satisfactory precision? • Sufficiently low statistical and systematic uncertainties? • What can be accomplished at the next level? • Are the sources of systematic uncertainties reducible? • Can the existing accelerator provide necessary statistical and systematic precisions? • Do we need a new accelerator? ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Discovered in 1995, ~170mp Directly observed in 2000 Standard Model Elementary Particle Table • SU3XSU(2)xU(1) gauge symmetry • Prescribes the following simple and elegant fundamental structure: • Total of 3 families of quarks and leptons with 12 force mediators form the entire universe ~0.1mp Family ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Are we all happy with the current theory? • Standard Model has been extremely successful under scrutinyEW sector tested very rigorously • Yet, there are outstanding issues lingering • Neutrino masses  Now proven that neutrinos oscillate • Electroweak symmetry breaking  Origin of mass • Search for the Higgs particle still on-going • CP violations  kTeV and other experiments • Why are there so wide a range in constituents’ masses (hierarchy problem)? • At what energy does the unification of all forces occur? • Is there any other model that describes nature better? • Will we find SUSY partner particles? • To answer these questions we need • The accelerator • The detector ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Current Status of Higgs Searches Most optimal central value is below the experimental limit under the SM ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Particle Accelerators • How can one obtain high energy particles? • Cosmic ray  Sometimes we observe 1000TeV cosmic rays • Low flux and cannot control energies or types of incident particles too well • Need to look into small distances to probe the fundamental constituents with full control of particle types, energies and fluxes • Particle accelerators • Accelerators need not only to accelerate particles but also to • Track them • Maneuver them • Constrain their motions better than 1mm • Why? • Must correct particle paths and momenta to increase fluxes and control momenta ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Role of Accelerators • Act as a probing tool • The higher the energy The shorter the wavelength • Smaller distance to probe • Take us back in time close to the creation of the universe • Two method of accelerator based experiments: • Collider Experiments: p`p, e+e-, ep • CMS Energy = 2sqrt(E1E2) • Fixed Target Experiments: Particles on a target • CMS Energy = sqrt(2EMT) • Each probes different kinematic phase space ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Particle Accelerator Types • Depending on what the main goals of physics are, one can use various kinds of accelerators • Fixed target experiments: Probe the nature of the nucleons (Structure functions) and measure particle properties • Results also can be used for producing secondary particles for further accelerations and beam particle selections • Colliders: Probes the interactions between fundamental constituents • Hadron colliders: Wide kinematic ranges and high discovery potential • Proton-anti-proton: TeVatron at Fermilab, Sp`pS at CERN • Proton-Proton: Large Hadron Collider at CERN (to turn on late 2009) • Lepton colliders: Very narrow kinematic reach and for precision measurements • Electron-positron: LEP at CERN, Petra at DESY, PEP at SLAC, Tristan at KEK, ILC in the med-range future • Muon-anti-muon: Conceptual accelerator in the far future • Lepton-hadron colliders: HERA at DESY ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Collider Accelerators – Lepton Collider • Used primarily for precision measurements • Particles without the internal structures - Point-like particles • Much lower total cross section than hadron colliders – Much cleaner final states • CMS energy for each collision well understood • Limited kimematic phase space • LEP, LEP-II, KEK, PEP-II, ILC ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Collider Accelerators – Lepton-Hadron • Primarily used for internal nucleon structure measurements • Point-like particle on a particle of structure • Can extend the kinematic space of the structure functions to very low momentum fraction • Needed for high energy experiments such as the LHC • Very asymmetric final state • DESY in Germany (HERA) ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Collider Accelerators – Hadron Collider • Primarily used as discovery machines • Collisions between structured particles • High total cross sections • Large number of events • Messy final states • From spectator quarks • Multiple interactions per collisions • Maximum kinematic reach for the given cost • Probes broad corners of kinematic phase space • CERN Sp`pS(0.63TeV), Tevatron (2TeV), CERN LHC (14TeV) ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Synchroton Accelerators • Synchrotons use magnets arranged in a ring-like fashion. • Multiple stages of accelerations are needed before reaching over GeV ranges of energies • RF power stations are located through the ring to pump electric energies into the particles ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Relativistic Variables • The invariant scalar, s, is defined as: • Show that in the CMS frame • In the CMS frame • Thus, represents the total available energy of the interaction in the CMS ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Jog-your-memory Simple Exercise • Derive the formulae for the available center of mass energy for • A fixed target experiment with incoming particle four momentum P1 (E1, P1) (E1>> m1)and the target mass of MT • A collider experiment with the two particle four momenta of P1 (E1, P1) and P2 (E2, P2) ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Particle Detectors • Subatomic particles cannot be seen with naked eyes but can be detected through their interactions within matter • What do you think we need to know first to construct a detector? • What kind of particles do we want to detect? • Charged particles and neutral particles? • What kind of particles are they? EM, Hadrons, Jets, neutrinos? • What do we want to measure? • Their momenta • Trajectories • Energies • Origin of interaction (interaction vertex) • Etc • To what precision do we want to measure? • Depending on answers to the above questions we use different detection techniques ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Tracking Devices • Used to provide the traces of charged particles resulting from interactions • Along with a magnet, provides the curvature of the charged tracks (charge ID) and their momenta • Used to determine the location of the interactions called vertices • Can provide secondary vertices resulting from the decay of longer lived particles • Some devices can measure energy losses of particles via radiations and provide additional particle ID information • Muon tracking system sits at the very outside for momentum measurement and identification ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

A Collider Experiment Tracking System (DØ) • 800k channel Si vertex detector • Provides precise location of the primary and secondary vertices • High resolution scintillating fiber tracking system • Provide high resolution position and momentum measurements ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Calorimeters • Magnetic measurement of momentum is not sufficient, why? • The precision for angular measurements gets worse as particles’ momenta increases • Increasing magnetic field or increasing precision of the tracking device will help but will be expensive • Cannot measure neutral particle momenta • Charge neutral particles do not leave traces in the tracker • How do we solve this problem? • Use a device that measures kinetic energies of particles • Calorimeter • A device that absorbs full kinetic energy of a particle • Provides the signal proportional to deposited energy • Can measure shower shapes with fine granularity • Must work as an integral part of the detector ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Calorimeters • Large scale calorimeter were developed during 1960s • For energetic cosmic rays • For particles produced in accelerator experiments • How do EM (photons and electrons) and Hadronic particles deposit their energies? • Electrons: via bremsstrahlung followed by a mixture of photon pair production and electron bremsstrahlung • Photons: via electron-positron conversion, followed by bremsstrahlung of electrons and positrons • These processes continue occurring in the secondary particles causing an electromagnetic shower losing all of its energy ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Interaction of Hadrons at High Energies • Hadronic collisions involve very small momentum transfers, small production angles and interaction distance of order 1fm • Typical momentum transfer in hadronic collisions are of the order q2 ~ 0.1 (GeV/c)2 • Mean number of particles produced in hadronic collisions grows logarithmically • ~3 at 5GeV • ~12 at 500GeV • High energy hadrons interact with matter, they break apart nuclei, produce mesons and other hadrons • These secondaries interact through strong forces subsequently in the matter and deposit energy ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Hadron Energy Deposit • Hadrons are massive thus their energy deposit via bremsstrahlung is small • They lose their energies through multiple nuclear collisions • Incident hadron produces multiple pions and other secondary hadrons in the first collision • The secondary hadrons then successively undergo nuclear collisions • Mean free path for nuclear collisions is called nuclear interaction lengths and is substantially larger than that of EM particles • Hadronic shower processes are therefore more erratic than EM shower processes • Slow neutron energy deposit also problematic ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Sampling Calorimeters • High energy particles require large calorimeters to absorb all of their energies and measure them fully in the device (called total absorption calorimeters) • Since the number of shower particles is proportional to the energy of the incident particles • One can deduce the total energy of the particle by measuring only fraction of their energies, as long as the fraction is known  Called sampling calorimeters • Most the high energy experiments use sampling calorimeters • Can measure E with much less detector volume … ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Hadron EM How do particle showers look in detectors? ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Calorimeter Design Considerations • Full shower containment • What are the expected energies of particles resulting from the interactions? • How deep and wide does the calorimeter have to be to contain full shower? • What is the necessary energy measurement precision? • What sensitive gap technology can allow to accomplish such precision? • At what longitudinal frequency do we need to sample? • What is the necessary longitudinal and transverse granularity? • What is the necessary position resolution? • What are the timing structure of the accelerator? • What are the particles to be identified in the detector? ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

What are the most distinguishing characteristics of different particles? • Electrons: Electromagnetic particle • Deposit virtually all of its energy in the electromagnetic section of the calorimeter • Has an associated charged track pointing at the cluster • Photons • Deposit virtually all of its energy in the electromagnetic section of the calorimeter • No charged track associated with it ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

What are the most distinguishing characteristics of different particles? • Hadronic particles, pions, Kaons, protons, neutrons, etc • Some have charge while some others don’t • Deposit energy throughout both EM and hadronic sections of the calorimeter • Hadroinc Jets induced from quarks and gluons • Multiple charged and neutral hadrons collimated like a jet • Deposit energies throughout the entire calorimeter section • Leave long and wide hadronic showers in the calorimeter • neutrinos: Does not interact in the calorimeter.. How do we measure its energy? • We measure its transverse energy using momentum imbalance ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Calorimeter (dense) Muon Tracks Charged Particle Tracks Energy Scintillating Fiber Silicon Tracking Interaction Point Ä B EM hadronic Magnet Wire Chambers Particle Detection and Identification electron photon jet muon We know x,y starting momenta is zero, but along the z axis it is not, so many of our measurements are in the xy plane, or transverse neutrino -- or any non-interacting particle missing transverse momentum ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

p `p Data Reconstruction Computers put together a picture Digital data PHYS 1441-002, Spring 2009 Dr. Jaehoon Yu

The NuTeV Detector • Physics goals • Beam characteristics • Detector requirements • NuTeV Calorimeter • NuTeV Calorimeter Performance ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

What are neutrinos? • Lepton species without electrical charge • Only affected by weak interactions, no EM • Have one helicity • we have observed only left-handed neutrinos and right-handed anti-neutrinos • This property led Yang & Lee to parity violation and eventually theory of weak interactions • No mass prescription in the original SM  Now some mass prescription corrections after the strong proof of neutrino oscillation • Measurements show three species only ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Physics With Neutrinos • Investigation of weak interaction regime • Only interact via weak interaction  This is why neutrinos are used to observe NC interactions • Measurement of weak mixing angle • Measurement of coupling strength e=gsinqW • Test for new mediators, such as heavy neutral IVBs • Measurement of SM r parameter • Indirect measurement of MW: sin2qW=r(1-MW2/ MZ2) • Measurement of proton structure functions • Measurement of neutrino oscillations ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Neutrino Cross Sections Charged Current Neutral Current ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Neutrino Experiments • Neutrino cross sections are small ~10-38 En • To increase statistics • Increase number of neutrinos • Natural or reactor sources will not give you control of beam intensity • Need man-made neutrino beams • Increase neutrino energy • Increase thickness of material to interact with neutrinos  Detectors with dense material • Beam can be made so that it is enriched with a specific flavors of neutrinos, such as nts. • How does one do this? ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

The NuTeV Experiment • NuTeV (E815) was a fixed target Deep Inelastic Scattering (DIS) experiment that used sign selected neutrino beams at Fermilab • Ran in the fixed target run at Fermilab 1996 – 1997 using 900 GeV protons hitting the target • NuTeV used an improved version of the beam lines and the detector from its previous incarnation, the CCFR experiment in the same beam line • NuTeV used a separate, dedicated beam line for constant in-situ detector calibration ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

NuTeV Scientific Goals • Measure sin2qW with a greater precision • Narrow down the Higgs mass range along with precise top quark mass measurements from other experiments • Beam line modification required • Need to understand the detector at a greater precision • Measure proton parton distribution functions to a greater precision • Provide precise knowledge on proton internal structure at high momentum fraction (x) and determine the strong coupling constant with higher precision • Good energy measurements • Good angle measurements ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Proton Structure Function Measurements • A complete set of Lorentz scalars that parameterize the unknown structure of the proton • Properties of the SF lead to parton model • Nucleon is composed of point-like constituents, partons, that elastically scatter with neutrino • Partons are identified as quarks and gluons of QCD • QCD does not provide parton distributions within proton • QCD analysis of SF provides a determination of nucleon’s valence and sea quark and gluon distributions (PDF) along with the strong coupling constant, as ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

nm,(`nm) m-, (m+) k k’ pm, qm W+(W-) q=k-k’ q, (`q) } xP EHad Partonic hard scatter P Non-perturbative, infra-red part Factorization Concept s=f*sp sp f ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

How Are PDFs Determined? • Measure n-N differential cross sections, correcting for target • Compare them with theoretical x-sec • Fit SF’s to measured x-sec • Extract PDF’s from the SF fits • Different QCD models could generate different sets of PDF’s • CTEQ, MRST, GRV, etc Fit to Data for SF ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

sin2qW and n-N scattering • In the electroweak sector of the Standard Model, it is not known a priori what the mixture of electrically neutral electomagnetic and weak mediator is This fractional mixture is given by the mixing angle • Within the on-shell renormalization scheme, sin2qW is: • Provides independent measurement of MW & information to pin down MHiggs via higher order loop corrections, in comparable uncertainty to direct measurements • Measures light quark couplings  Sensitive to other types (anomalous) of couplings • In other words, sensitive to physics beyond SM  New vector bosons, compositeness,n-oscillations, etc ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

How is sin2qW measured? (or e) • Cross section ratios between NC and CC proportional to sin2qW • Llewellyn Smith Formula: ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Sources of Neutrinos:Atm and other • High energy cosmic-ray (He, p, n, etc) interactions in the atmosphere • Cosmic ray interacts with air molecules • Secondary mesons decay • Muons decay again in 2.6ms • Neutrinos from Big Bang (relic neutrinos) • Neutrinos from star explosions • Neutrinos from natural background, resulting from radioactive decays of nucleus • Neutrinos from nuclear reactors in power plants ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Beam Characteristics – NuTeV • Fermilab’s Fixed Target beam using 900GeV protons hitting the target to generate neutrinos • How can we produce neutrino beams? ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Good beam focusing Good target Sufficient dump p Long decay region Conventional Neutrino Beam • Use large number of protons on target to produce many secondary hadrons (p, K, D, etc) and focus them well • Let p and K decay in-flight for nm beam • pm+nm(99.99%), Km+nm (63.5%) • What percentage of pions will decay in the 540 m decay region when their mean energy are 150GeV? • Other flavors of neutrinos are harder to make • Let the beam go through shield and dirt to filter out m and remaining hadrons, except for n • Dominated by nm ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Improving Experimental Uncertainties • Electron neutrinos, ne, in the beam fakes NC events from CC interactions • If the production cross section is well known, the effect will be smaller but since majority come from neutral K (KL) whose x-sec is known only to 20%, this is a source of large experimental uncertainty • Need to come up with a beamline that separates neutrinos from anti-neutrinos ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Beam Characteristics – NuTeV • Fermilab’s Fixed Target beam using 900GeV protons hitting the target to generate neutrinos • How can we produce neutrino beams? • How can we produce neutrino beams of specific signs (n or `n)? ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

How can we select sign of neutrinos? • Neutrinos are electrically neutral • Need to select the charge of the secondary hadrons from the proton interaction on target • NuTeV experiment at Fermilab used a string of magnets called SSQT (Sign Selected Quadrupole Train) • Proton beam shot with a 7mr upward incident angle • Dipoles immediately behind the target bends the particles of right signs toward the detector • Wrong charge particles and the remaining protons are dumped ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Beam Characteristics – NuTeV • Fermilab’s Fixed Target beam using 900GeV protons hitting the target to generate neutrinos • How can we produce neutrino beams? • How can we produce neutrino beams of specific signs (n or `n)? • Two different beam lines used • Neutrino beam: Fermilab’s NC (Neutrino Center) • 5 “pings” of widths 5 ms separated by 0.5 seconds • Calibration Beam: NT (Neutrino Test) • A 18 second slow spill of continuous beam 1.8 seconds after the last short pulsed neutrino beam ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Event Length y-view Charged Current Events Nothing is coming in!!! m x-view m y-view Neutral Current Events Nothing is coming in!!! Nothing is going out!!! x-view How Can Events be Separated? ILC Calorimeter School, Tsinghua University J. Yu, Univ. of Texas at Arlington

Calorimeters In Action!!