  The measurement of sparticle masses in the Minimal Supersymmetric Standard
Model at the LHC is analysed, in the scenario where the lightest neutralino
decays into three quarks. Such decays, occurring through the baryon-number
violating coupling lambda"\_ijk, pose a severe challenge to the capability of
the LHC detectors since the final state has no missing energy signature and a
high jet multiplicity. We focus on the case of non-zero lambda"\_212 which is
the most difficult experimentally. The proposed method is valid over a wide
range of SUGRA parameter space with lambda"\_212 between 10^{-5}-0.1.
Simulations are performed of the ATLAS detector at the Large Hadron Collider.
Using the lightest neutralino from the decay chain left-squark to quark +
next-to-lightest neutralino to right-slepton + lepton + quark and finally to
lightest neutralino + lepton pair + quark, we show that the lightest and
next-to-lightest neutralino masses can be measured by 3-jet and 3-jet + lepton
pair invariant mass combinations. At the SUGRA point M_0=100 GeV, M_{1/2}=300
GeV, A_0=300 GeV, tan beta=10, sign of mu positive and with lambda"\_212=0.005,
we achieve statistical (systematic) errors of 3 (3), 3 (3), 0.3 (4) and 5 (12)
GeV respectively for the masses of the lightest neutralino, next-to-lightest
neutralino, right-slepton and left-squark, with an integrated luminosity of 30
fb^{-1}.
