Beyond the Large Hadron Collider: R&D Towards an International Linear Collider Bruce Schumm SCIPP & UC Santa Cruz San Jose State Physics Seminar April

First: CPAPC Initial contact made (Schumm to Parvin) with respect to joint CSU/UC initiative to promote graduate study in physics CPAPC = “California Professoriate for Access to Physics Careers” CPAPC is in a state of formation… Seminars Learning about UC PhD programs (UC faculty sponsors?) Research opportunities ??? (some funding ideas being explored, e.g. NSF S-STEM) Anyway, back to the ILC…

“We recommend that the highest priority of the U.S. program be a high-energy, high-luminosity electron-positron collider, wherever it is built in the world. This facility is the next major step in the field, and should be designed, built, and operated as a fully international effort.” Fall 2001 recommendation of the High Energy Physics Advisory Panel (HEPAP) to the Department of Energy’s Office of Science: The ILC group at SCIPP has been undertaking an ever- growing list of R&D studies, making use primarily of students (1 grad, 8 physics and 1 computer engineering undergrads, and even a high school student!) As a result, a Global Design Effort has been formed, led by CalTech’s Barry Barish. Currently targetting 2012 for a design report, including detectors.

TESLA NLC

ILC Detectors Tracking Volume (charged particles only Calorimetry (total absorption): charged and neutral

The International Linear Collider is expected to: Collide electrons (matter) with positrons (antimatter) at energies up to 500 GeV (about 2 ½ times greater than prior record) Run after the Large Hadron Collider, at a lower energy  measurements characterized by precision and elegance rather than brute-force discovery Be built somewhere on planet Earth (Hamburg? Chicago? Japan?) if some country comes up with ½ the price tag Explore the properties of the Higgs (enigmatic undiscovered “Standard Model” particle) if it’s there, or what acts in its stead if not Explore the properties of Dark Matter if any one of several popular scenarios are correct (Supersymmetry!)…

The Higgs “Natural” theory: all these particles are massless Harsh reality: None of these particles is massless (except the photon) Solution: The Higgs field

How The Higgs Works (in so many words…) Think of moving a pole through a pond of molasses. The fatter the pole, the greater resistance the pole will feel  the greater intertia, by which I mean mass the pole will seem to have Heavier particles aren’t really heavy, they just have a larger drag against (or higher cross-section within) the ever-present Higgs field. So, no mass – it’s just an illusion presented by this Higgs-field drag (yay for the theorists!)

But What is the Higgs Particle? Oh – by the way, if you drop one of the poles (particles) into the pond from a great enough height (with enough energy), you will create waves that propagate along though the pond (through space). But in Quantum Mechanics, propagating waves are known as particles. So if all this is right, we ought to be able to create a new particle assoaciated with the “molasses”; the Higgs particle Also, if so, the properties of the Higgs will be precisely predicted (e.g. how it decays to other particles)  precision studies essential!

Shameless Plug If you want a more rigorous, discussion of all this, might I suggest… Oscar Wilde: “For people who like this sort of thing, this is the sort of thing they like” Available at all the none of the finest bookstores (try Amazon)

Studying the Higgs at the ILC electronpositron Higgs “Z” (well-known particle) muons (  ); also well-known ?  we’d love to know what this stuff is! First, measure the muons to find the energy of the Z

Mass of system recoiling against the Z (GeV) Accuracy (momentum resolution) is essential Not so good detector Good detector

B = 5 Tesla Collision Point Cross-section of typical tracking system (“SiD” Detector Concept

x x x x x x Viewing detector end-on Momentum is determined by radius of curvature R in the 5 Telsa B-field

Silicon Micro-Strip Detectors With strips separated by 50  m, low readout noise, and combining information from neighboring channels, expect to measure azimuthal coordinate to  5-7  m This is needed for “good detector” performance. A challenge!

50  m Pulse development in silicon microstrip sensors: accuracy comes from taking weighted average of signals on neighboring strips Biggest signal used to indicate passage of particle (not just noise from one of 10 million strips!) Smaller neighboring signals used to pinpoint where particle was half-way through sensor  Electronic readout noise must be minimal! 300  m

Application-Specific Electronics (the LSTFE front-end chip)

Design: 0.25  m CMOS; long (3  s) shaping time limits noise Two “comparators”: can dig out small neighboring signals

1/4 mip 1 mip 128 mip Operating point threshold Readout threshold High gain advantageous for overall performance (channel matching)

FPGA-based control and data- acquisition system “LSTFE” (Long Shaping-Time Front End) chip mounted on readout board

Pulse-height measured by Time- Over-Threshold (TOT), not by integrating and digitizing! Omar Moreno LSTFE Pulse-Height Measurement

FIFO (Leading and trailing transitions) Low Comparator Leading-Edge-Enable Domain Proposed LSTFE Back-End Architecture Clock Period  = 400 nsec Event Time 8:1 Multi- plexing (  clock = 50 ns)

Generic Studies of Readout Noise

Standard Form for Readout Noise (Spieler) Series Resistance Amplifier Noise (series)Amplifier Noise (parallel) Parallel Resistance F i and F v are signal shape parameters that can be determined from average scope traces.

LONG LADDER CONSTRUCTION

Readout Noise Results Have explored end and “center-tap” readout (from center of chain rather than end).  Results are promising… but why? Naïve expectation Expectation with measured shape factors F i, F v Measured (end readout) Measured (center-tap) Kelsey Collier

Charge Division for Silicon Strip Sensors

Have left out a lot of ILC Physics Dark matter/supersymmetry Symmetry breaking (masses!) if Higgs isn’t there Top quark physics Extra dimensions Precision studies of Standard Model particles …

And a lot of SCIPP ILC activity LSTFE chip Readout noise Charge division Short strip alternatives (SLAC “KPiX”) Detector design simulation studies CLIC studies (even higher energy!) Radiation damage studies But hopefully this gives a flavor of what we are doing (not so far!) over the hill…