CKM Group at University of Virginia

The CKM Group at University of Virginia

The Fermilab CKM web page.
CKM at Work - The UVa CKM group's work space (password protected).
Useful information
CKM Monte Carlo Simulation
UMS bible
BTSM bible
Some photos

The Physics of CKM Charged Kaons at the Main Injector, or CKM is a major new Fermilab experiment. The primary goal of CKM is to test the hypothesis that the sole source of matter-antimatter asymmetries, or CP violation, lies with the imaginary phase of the Cabibbo, Kobayashi, Maskawa matrix (CKM) which describes the couplings between the u,c,t and d,s,b quarks. This will be done by a precision measurement of the CKM matrix element V_td through the super-rare decay: K⁺ → π⁺ νν (expected to occur only once every 10 billion decays!). The experiment was approved in June, 2001. It is a major new initiative --- has a cost of approximately $70 million --- and is expected to "form the core of a 120 GeV fixed target program" at Fermilab. Indeed, to date it is only one of two fixed-target experiments that have been approved at Fermilab.

The evidence for this decay mode has recently been published by experiment E787 at Brookhaven National Laboratory (BNL). They reported the observation of one event with an expected background of 0.08 +- 0.03 events and quote a branching ratio of {1.5(+3.4)(-1.2)} x 10^-10. The next important step is a measurement of this rate with sufficient precision to quantitatively challenge the Standard Model interpretation of the source of CP violation. The CKM is a decay in flight experiment in contrast to the stopped kaon technique used at BNL.

The CKM Spectrometera Measuring a branching ratio of 1x10^-10 to a 10% precision is a daunting task and requires a high-rate spectrometer with a background rejection below 10^-11. The collaboration has designed a unique spectrometer whose salient features are extremetly high-rate capability and high redundancy.

UVa's Responsibilities The UVa Antimatter Asymmetry Group significant hardware and software responsibilities in CKM. These include:

The design and construction of the Upstream Magnetic Spectrometer (UMS).
The design and construction of the front-end electronics.
The design and construction of the Beam Time Stamp Module (BTSM).
The simulation of the UMS and Kaon Entrance Angle Tracker (KEAT).

Note that our UMS wire chamber design for the UMS has been adopted for the Kaon Entrance Angle Tracker (KEAT). To facilitate this work we have made significant upgrades to our CAD capabilities, with the purchase of a high-end, PC-based CAD station and a 42" wide high-resolution plotter, as well as the purchase of a DAQ computer. We have also continued our extensive simulation work which has included: setting up a detailed GEANT-based simulation of the UMS and KEAT, writing a tracking program for both detectors, and various studies such as the feasibility of a silicon tracker.

The UMS must make a precise measurement of the momentum of the incident beam particles in a very high rate environment: 50 million charged particles will course through it every second. It employs six extremely high-rate, low-mass, narrow-pitch wire chambers. The PWC's needed for the UMS will not be simple to fabricate. With a 0.8mm pitch, they will push the limit of what has been achieved in the past, including the high-rate HyperCP wire chambers. Work is in progress designing these state-of-the-art chambers: we hope to have a prototype fabricated by this summer. The particles leaving the RF-separated beam line and to measure the direction of the particles incident on the Kaon RICH. The BTSM is used to tag the time of each beam track with a precision of about 1ns. Meanwhile the purpose of KEAT is to measure the angular resolution to accurately tie the incoming kaon track to the pion track from the decays of K⁺ → π⁺ νν.

Back to main page