The Sensex is likely to open in the positive zone and continue its upmove. The index however may face stiff resistance around 11,800 levels.The index is likely to face resistance around 11,750-11,775-11,800 levels. On the downside, the index may find support around 11,575-11,550-11,520 levels.According to market analyst Bharat Momaya, the Sensex is expected maintain its upward momentum as the tax collection data for first five months of current fiscal is encouraging.He adds that 'expectations about second quarter results are better and shall lift market sentiments upwards. Huge accretion to foreign exchange reserves in the current week is also positive for the market. Official clarification from Ministry of Finance about Participatory Notes will also help market sentiment'. 'Taxation laws are likely to be overhauled and simplified by 1st April, 2008. Reduction in tax rates can be expected in new regime. Proposal from government of Maharashtra about Octroi abolition is encouraging', Momaya added. He concludes, overall, the Sensex is likely to remain in positive territory and may cross the 12K mark in coming days. Intraday traders should watch their positions closely as Sensex may show sudden vertical and sharp upmoves. Short-sellers should remain most vigilant.