To the Terascale The ILC opportunity
P. GrannisFermilab, Oct.18, 2006 To the Terascale The ILC opportunity Talk on case for LC in Jan 2001 was compared to an unsavory politician for suggesting an e+e- collider was the wave of the future for Fermilab.Now, I am probably being criticised for not helping the lab move ahead on ILC fast enough! Fix page #s We are confident that new understanding of matter, energy, space and time can be gained through experiments at the TeV scale Bill Gates spell check for Terascale: Treacle Erasable
Teacake Treacle 1 : a medicinal compound formerly in wide use as a remedy against poison 2 chiefly British a : MOLASSES The Terascale frontier
49 The Terascale frontier Increasing energy of particle collisions in accelerators corresponds to earlier times in the universe, when phase transitions from symmetry to asymmetry occurred, and structures like protons, nuclei and atoms formed. The Terascale (Trillion electron volts), corresponding to 1 picosecond after the Big Bang when the EM and Weak forces diverged, is special.We expect dramatic new discoveries there. The ILC and Large Hadron Collider (LHC) are like telescopes that view the earliest moments of the universe. 48 The Standard Model Over 30 years, the SM has been assembled and tested with 1000s of precision measurements. No significant departures at the particle level. Strong and unified EM and Weak forces transmitted by carriers gluons, photon and W/Z. Though very different at everyday energies, EM and Weak forces are similar at very high energy and merge to a single Electroweak force.The SM breaks the symmetry by introducing a Higgs field that gives mass to the W and Z bosons (and quarks and leptons).A single Higgs particle survives with mass ~ GeV, waiting to be found. The Standard Model is flawed
47 The Standard Model is flawed The SM cant be the whole story: Quantum corrections to Higgs mass (& W/Z mass) would naturally drive them to the Planck (or grand unification) scale.Keeping Higgs/W/Z to ~ of Planck mass requires extreme fine tuning (hierarchy problem) or new physics at Terascale. Strong and EW forces are just pasted together in SM, but are not unified.New Terascale physics could fix this. 26 bizarre and arbitrary SM parameters are unexplained (e.g. why are n masses ~10-12 times top quark mass, but not zero?.If the up quark were heavier than the down quark no free proton, no H atom, no stars, no us.) SM provides CP violation, but not enough to explain asymmetry of baryons and antibaryons in the universe. And we now have the tools to get there !
46 The Terascale terrain There is non-SM physics in the universe at large: Gravity remains outside the SM Dark Matter is seen in galaxies and is needed to cluster galaxies in the early universe.It appears to be a heavy particle (or particles) left from the Big Bang, with mass in the Teravolt range. Unexplained Dark Energy is driving the universe apart.It may be due to a spin zero field, so study of the Higgs boson (the only other suspected scalar field) may help understand it. New physics is needed at the Terascale to solve or make progress on these puzzles.There are many theoretical alternatives, so experiment is needed to show us the way. And we now have the tools to get there ! 45 The LHC Mt. Blanc The 14 TeV (ECM), 27 km circumference LHC proton-proton Collider at CERN on the Swiss-French border complete in The LHC will be the highest energy accelerator for many years. Lake Geneva But The protons are bags of many quarks and gluons (partons) sharing the proton momentum.Parton collisions have a wide range of energies up to ~5000 GeV.Initial angular momentum state is not fixed. parton momentum fraction, x Proton collisions 2 partons within the protons scatter
Two protons approach each other, each with 7 TeV of energy The partons fragment into a jet of observed particles Each carries only a fraction of the proton energy The International Linear Collider
44 The International Linear Collider Collide e+ and e- beams with fixed energy, tuneable up to 250 GeV (upgrade to 500 GeV); Ecm =2Ebeam. Two linear 10 (20) km long linear accelerators. 90% polarized electron source; positrons formed by gs from helical undulator creatinge+ (could be polarized to 60%) Damping rings to produce very small emittance beams. Final focus to collide beams (few nm high) head on. Layout of electron arm Scientific case for the ILC
43 Scientific case for the ILC The ILC will be very expensive and thus the scientific justification must be very strong. The Quantum Universe report gives nine key questions. LHC and ILC will illuminate most. I. Einsteins dream Undiscovered principles, new symmetries? What is dark energy? Extra space dimensions? Do all forces become the same? II. The particle world New particles? What is dark matter? What do neutrinos tell us? III. Birth of universe How did the universe start? Where is the antimatter? The LHC should show us there is new physics at the Terascale. The ILC should tell us what it really is.The LHC and ILC are highly synergistic each benefits from the other. 41 Revealing the Higgs (1) W W W Higgs The Higgs field pervades all of space, interacting with quarks, electrons W, Z etc. These interactions slow down the particles, giving them mass. The Higgs field is somewhat like the Bunraku puppeteers, dressed in black to be invisible, manipulating the players in the drama. A SM Higgs is experimentally ruled out by LEP below 115 GeV.The virtual effects on W, top quark masses and Z decays rule out SM Higgs above ~200 GeV.Something must intervene by 1 TeV to preserve unitarity in WW scattering.Tevatron or LHC should discover Higgs. 39 Revealing the Higgs (2) LHC can discover Higgs with any mass to >1 TeV.The ILC sees the Higgs in unbiassed manner by observing the recoiling Z. e+ e- Z Higgs (Measure Z) (Infer Higgs) The LHC will not determine Higgs spin and parity. ILC can. Rare process e+e- ZHH measurable at ILC, yielding Higgs coupling to itself a crucial test of SM.Final state is 6 jets. e+ e- Z Higgs Isolating this process from background places very stringent requirements on the jet energy resolution in the calorimeter. 38 Revealing the Higgs (3) In the SM, Higgs couplings are directly proportional to mass.In extensions to SM, couplings are different.Measuring these couplings is a sensitive test of what the real model is. In the clean environment of the ILC, can distinguishHiggs decays to b, c, and light quarks; e, m, t; and W, Z .And can measure the Higgs coupling to itself. Coupling to Higgs 2 sample non-SM models String inspired supersymmetry 1.2 SM prediction 1 0.8 Ratios of BRs to SM Measuring the Higgs BRs set a key criterion for ILC detectors a very finely grained Si vertex pixel detector at small radius. Decoding Supersymmetry (1)
By introducing fermion and boson partners, Supersymmetry theoretically solves many of the SM defects:hierarchy problem, possible unification of EW and Strong, low mass Higgs and has a good dark matter candidate.There is no experimental confirmation at present! LHC will discover Supersymmetry if it has anything to do with EWSB. Solving these SM ills comes at a price Supersymmetry itself is a broken symmetry (there is no spin 0 electron partner at MeV). Understanding the Supersymmetry model and symmetry breaking will require the ILC. Particles and sparticles same Q#s, but one is spin 0 and other is spin . Decoding Supersymmetry (2)
~ m- g,Z ILC can measure sparticle masses to very high precision, particularly partners of leptons, W,Z,g. e.g. Pair produce the partners of muons, with decay m m c0. (c0 is neutralino typically the lightest, stable Susy particle DM candidate). ~ The sharp edges in decay m energy distribution pin down the c0 and m mass to 0.05% accuracy.Their spins (the key Susy signature) are also determined. ~ Two sample Susy breaking models different patterns. These precise masses and LHC information allow extrapolate Susy parameters to high energy and infer the Susy-breaking mechanism. Energy Decoding Supersymmetry (3)
About 80% of matter in universe is dark possibly a heavy relic particle from the Big Bang.c0 is an excellent candidate.Planck satellite will measure DM density accurately.ILC (and LHC) can measure DM mass and density. DM mass Maybe ILC agrees with Planck; then the neutralino is the only dark matter particle. DM density Maybe ILC disagrees with Planck; this would tell us that there are different forms of dark matter. Perhaps the neutralino and its partners violate CP symmetry to the extent needed for baryon-antibaryon asymmetry in the universe.ILC could uncover this. Finding extra spatial dimensions (1)
29 Finding extra spatial dimensions (1) String theory requires at least 6 extra spatial dimensions (beyond the 3 we already know).The extra dimensions are curled up like spirals on a mailing tube. If their radius is large (>1 attometer = 10-9 of atomic diameter), they could unify all forces (including gravity) at a reduced Planck scale at O(TeV). If a particle created in an energetic collision goes off into the extra dimensions, it becomes invisible in our world and the event shows missing energy and total momentum imbalance detectable in LHC or ILC experiments. Our 3-d world Finding extra spatial dimensions (2)
27 Finding extra spatial dimensions (2) There are many possibilities for the number of large extra dimensions, their size and metric, and which particles can move in them.LHC and ILC see complementary processes that will help pin down these attributes. collision energy (TeV ) The LHC collisions of quarks span a range of energies, and therefore measure a combination of the size and number of the large extra dimensions. Different curves are for different numbers of extra dimensions production rate The ILC with fixed (but tuneable) energy of electron- positron collisions can disentangle the size and number of dimensions individually. Finding extra spatial dimensions (3)
26 Finding extra spatial dimensions (3) dimuon mass prouction rate Wavefunctions trapped inside a box of extra dimensions yields a series of resonance states that decay into e+e- or m+m- (like a new Z boson). But other new physical mechanisms could provide similar final states.LHC will not tell us what the new particle is. axial coupling The ILC can measure the two ways (vector and axial vector) this particle interacts with electrons. The colored regions indicate the expectation of 3 possible theories; the ILC can tell us which is correct! vector coupling ILC error Seeking Unification go here sense whats happening here Present data show that the three forces (strong, EM, weak) have nearly the same strength at very high energy indicating unification?? Closer look shows its only a near miss! g2 g3 Supersymmetry at TeV scale allows forces to unify at GUT scale. g1 The elements of detectors
23 The elements of detectors The basic structure of detectors is the same for LHC and ILC : nested subsystems covering DW ~ 4p Fine segmentation Si pixel/strip detectors to measure displaced decay vertices (b and c quark identification) Tracking detectors in B-field to measure charged particle momenta EM calorimeter to identify, locate and measure energy of electrons & photons Hadron calorimeter for jet energy measurement Muon detectors outside the calorimeter The LHC CMS and ILC SiD detectors
22 The LHC CMS and ILC SiD detectors To theorists and general public, the detectors look pretty much alike.To the experimenters, like proud parents, each is unique and lovely. SiD concept And the ILC detectors present some special challenges. ILC vertex detector needs
20 ILC vertex detector needs Silicon pixel and strip detectors arranged in barrels and disks, starting at about 15 mm from the beam line (have to stay outside the intense flood of e+e- pairs from bremsstrahlung in field of opposing beam). Hits in vertex detector allow recognition of long-lived particles (b, c quarks and t lepton) SiD vertex detector design concept (Norman Graf) c decay vertex b decay vertex primary vertex 19 ILC calorimeter needs Desire to separate W and Z to 2 jets at ILC requires very good energy resolution.Do this by using magnetic measurement of charged particle energy and calorimetric measure of neutrals.Need to separate the energy clusters for charged and neutral in calorimeter fine segmentation. DE/E=60%/E DE/E=30%/E r + p+ p0 (p0 g g ) Particle flow calorimetry has yet to be demonstrated experimentally. Experiment environment at LHC
18 Experiment environment at LHC LHC Background events due to strong interactions are large: Total inelastic cross section = 8x1010 pb XS x BR for Z mm = 2x103 pb XS x BR for 120 GeV Higgs (H gg) = 0.07 pb Signal to background for interesting events is small. Require sophisticated trigger to select interesting events. 100s of particles produced: event reconstruction is a challenge. Large event rate gives event pileup and large radiation dose. LHC detectors are very challenging Experiment environment at ILC
17 Experiment environment at ILC Rate of collisions is rather low (good for backgrounds, bad for high statistics studies), and number of produced particles is typically small. Total e+e- annihilation XS (500 GeV) = 5 pb e+e- ZZ cross section = 1 pb e+e- ZH cross section = 0.05 pb Signal to background for interesting events is large. Precision studies at ILC require excellent jet energy and spatial resolution, and precise measurement of long lived decay vertices. ILC detectors are very challenging 16 Why a linear collider? Particle physics colliders to date have all been circular machines (with one exception SLAC SLC). Highest energy e+e- collider was LEP2: ECM=200 GeV Synchrotron light sources are circular As energy increases at given radius DE ~ E4/r(synchrotron radiation) e.g. LEP DE=4 GeV/turn; P~20 MW High energy in a circular machine becomes prohibitively expensive large power or huge tunnels. Go to long single pass linacs to reach desired energy. Collide the beams just once (but electrons are cheap!) Energy cost Linear Collider Circular Collider ILC is here ILC baseline configuration
~31 km RTML ~1.6km 14mr BDS 5km ML ~10km (G = 31.5MV/m) e+ 150 GeV (~1.2km) R = 955m E = 5 GeV Not to scale 2 x 250 GeV linear accelerators using superconducting rf (31.5 MV/m). Positrons (upgrade to polarized e+) made from gs radiated in undulator, striking a conversion target. 6 km circumference Damping Rings to provide small emittance. Two interaction points, 14 mrad crossing angle; 6 nm high beams. Plan for upgrade to 500 GeV beams (ECM = 1 TeV). With backscattered laser light, can produce gg collisions ~80% of e+e- energy. Baseline is evolving under change control L = 2 x 1034 cm-2 s-1 ILC parameters Bunch spacing 337 ns
14 ILC parameters Bunch spacing337 ns Bunch train length950 ms Train rep rate5 Hz Beam height at collision6 nm Beam width at collision540 nm Accel. Gradient MV/m Wall plug effic.23% Site power (500 GeV)~200 MW L = 2 x 1034 cm-2 s-1 105 annihilations/sec A parameter plane:vary bunch charge, # bunches, beam sizes to allow a flexible operating plane. Source, damping ring Interaction pt.beam extraction Accelerating the beams
13 Accelerating the beams Accelerating structures
12 Accelerating structures Ez c Travelling wave structure; need phase velocity = velectron = c Circular waveguide mode TM01 hasvp> c ;no good for acceleration! Need to slow wave down to phase velocity = c, using irises. Bunch sees constant field Ez=E0 cosf Group velocity < c, controls the filling time in cavity. z SC cavity 11 RF distribution Modulator (switching circuit) turns AC line power into HV DC pulse. Multibeam klystron (RF power amplifier) makes 1.4 ms pulses at 1.3 GHz MW pulse power.Need ~700. The heart of the linac: Pure Nb 9-cell cavity operated at 2K; ,000 cavities: 31.5 MV/m accel. gradient. Issues for SC accelerating structures
10 Issues for SC accelerating structures Learning how to prepare smooth pure Nb surfaces to get the high gradient was a decade-long effort.Recent advance uses electropolishing as well as chemical polishing for smooth surface. Alternate cavity shapes have reached >50 MV/m. But the process is not under good control.One still worries about field emission from surface imperfections giving large dark current. Slide showing all Tesla cavities with EP to date to dramatize problem; OMB slide on what is needed for SCRF test facilities SC specification on gradient and Q value.Now exceeding spec, but large spread in gradient and poor reproducibility. Achieving the luminosity (keeping the beam emittances small)
9 Achieving the luminosity (keeping the beam emittances small) Create small emittance beams in damping rings before the main linacs allow synchrotron radiation to reduce all three components of particle energy; restore longitudinal momentum with RF acceleration. (To keep the DR circumference small (6km) the 300 km long bunch train is folded on itself.) 8 Damping rings Must keep very careful control of magnet alignment, stray B fields, vacuum, instabilities induced by electron cloud (in e+ rings) or positive ions (in e- ring) to avoid emittance dilution.Need a very fast kicker to inject and remove bunches from the train in the damping rings. Prototype damping ring has been built in KEK (Japan) and achieved necessary emittance.The 6ns kickers now exist. 7 Wake fields Wakefields:Off axis beam particles induce image currents in cavity walls; these cause deflections of the tail of the same bunch, and perhaps on subsequent bunches. Betatron oscillation in head of bunch creates a wakefield that resonantly drives the oscillation of the tail of same bunch.Can be cured by reducing tail energy; quads oversteer and compensate for beam size growth. head tail Beam growth due to single bunch wakefield amplitude Wakefield effects on subsequent bunches die out in the long bunch time interval (337 ns), so not a problem. z Making an international project
6 Making an international project Herding cats: how do we organize the ILC so that all regions of the world feel that they are full partners and gain from participation? What kind of organizational structure? How to set the site selection process? How to account for costs and apportion them? Organizing the alphabet soup
5 Organizing the alphabet soup International Linear Collider Steering Committee (ILCSC) (2002): Set basic physics specifications (2003) Made choice among competing technologies (for SC RF) (2004) Established Global Design Effort =GDE (2005) virtual world lab with balanced Asian, European, Americas participation to do design, manage R&D, cost estimate.Barry Barish is Director. GDE established the baseline design parameters in 2005; is preparing Reference Design and cost estimate during 2006. Funding Agencies Linear Collider (FALC) is science minister level group formed in FALC is discussing the organizational model, rules for site selection, timetable for government consideration of the full ILC project. expression of interest
4 The GDE schedule LHC Results off ramp Global Design Effort Project Baseline configuration Reference Design/ initial cost Technical Design globally coordinated regional ILC R&D Program expression of interest Siting sample sites Hosting International Management ILCSC FALC ILC Lab The ILC in the US context
3 The ILC in the US context ILC is US highest priority for new initiative (HEPAP);DOE put ILC at top of list for intermediate term, and expressed interest in hosting ILC at a site near Fermilab. Administrations ACI initiative would double DOE SC, NSF, NIST core research in 10 years, with focus on areas of maximum economic impact.But even for basic research, the outlook has brightened. National Academy panel (Apr report Revealing theHidden Nature of Space and Time) with significant participation of non-physicists concludes:US should be a leader in high energy physics, and advocates an optimum strategy that pursues vigorous R&D on ILC and seeks to host in US. 2 ILC cost The ILC cost is not a well defined term; each nation has its own costing rules (include labor? contingency? overheads? R&D? inflation?) and materials and labor costs vary.Taking the estimate for the 500 GeV TESLA project of $3.1B; add salaries, contingency, overheads, detectors to get $10B in USterms: Divide by 3000 physicists (those signing the consensus document) and by 25 years for building + initial operation project duration: Cost per physicist/year = $130,000 ILC cost will be done as for ITER in terms of value units basic materials and some value of manpower.Host country takes ~50%; other nations bid for their desired pieces apportioned by value share. Conclusions We know the terascale is fertile ground for newdiscoveries about matter, energy, space and time. We strongly believe there is a new playing field where there are new phenomena but we dont know yet the players or rules of the game. The ILC allows precision measurements that will tell us the true nature of the new phenomena. The ILC and the LHC together provide the binocular vision needed to see the new physics in perspective, and thus probe the earliest times in the universe. Experiment environment at ILC
18 Experiment environment at ILC In the ILC the beam e+ and e- are the colliding partons, so the collision energy is the full e+e- energy and can be accurately controlled .But require different energy settings for producing different particles. Initial state is fixed (JP=1-).The e can be polarized, thus enhancing or suppressing signal or background reactions. Small angle region contains intense flux of e+e- pairs radiated by the EM fields of the beams. Can place detectors close to the beams. 25 Seeking Unification Einsteins greatest dream was finding unification of the forces. The LHC and ILC together will provide the precision measurements to tell us if grand unification of forces occurs. The ILC can provide a connection to the string scale where gravity may be brought in. Precision measurements at the Terascale provide the telescope for charting the very high energy character of the universe, instants after the Big Bang. Understanding dark matter
An aside:at the LHC, the mass of the neutralino and its heavier cousins (such as the c20) are entangled.LHC cannot measure the higher mass states accurately as it does not see the c10. c20 mass error with ILC help c20 mass The precise ILC neutralino mass measurement allows the LHC to pin down the other particle mass a typical example of the synergy of the ILC and LHC.Measurements at one accelerator enable improvements at the other. c20 mass error with no ILC help LHC measurement neutralino mass The GDE organization FALC ICFA FALC Resource Board ILCSC GDE
Directorate GDE Executive Committee GDE R & D Board GDE Change Control Board GDE Design Cost Board Global R&D Program RDR Design Matrix Revealing the Higgs Higgs self couplings a key feature of the SM or its extensions. Sombrero plot and HHH coupling diagram and limits.Sets the other key requirement for ILC detectors on jet energy resolution:PFA (separate slide). Top Yukawa coupling:at 500 GeV, LHC measures the rate of Htt with H to bb. ILC adds the bb BR so together they get the top coupling. At 1000 GeV, ILC directly measures the ttH to give xx precision.