Credit-checking firm Experian was a high riser after unveiling an unexpected $600m share buyback and outlining plans to "deliver annual average growth in organic revenue in the mid-single digit range". The company also said it has the potential for "strong growth" in earnings per share.Copper miner Antofagasta was in the red after announcing that it expected a weaker production output for 2015 than initially anticipated. "This is unlikely to give any confidence to the investors who, in our view, were expecting annual improvement in unit costs due to a weak Chilean peso and lower oil prices," Citi analysts said in an emailed statement on Wednesday.Mining giant Anglo American was boosted after meeting forecasts with its fourth-quarter output results with improvements in iron ore, coal and platinum and declines in copper, nickel and diamonds. With shares trading near 10-year lows, analysts at Société Générale said the shares did not seem to reflect a likely recovery in commodity prices .Chip designer ARM Holdings was trading higher after better-than-expected results from customer Apple showed strong demand for smartphones.Third-quarter sales rose at Johnson Matthey but shares slumped after the chemicals group's underlying profits growth slowed due to continuing issues with Anglo American Platinum.Business management software group Sage underwhelmed and was lower after saying it made only a "solid start" to the new financial year and remains on track to hit its growth targets. RisersWeir Group (WEIR) 1,688.00p +2.93%Experian (EXPN) 1,199.00p +2.92%SABMiller (SAB) 3,532.00p +2.79%Anglo American (AAL) 1,111.50p +1.97%ARM Holdings (ARM) 1,049.00p +1.75%Capita (CPI) 1,110.00p +1.56%TUI AG Reg Shs (Post- 16/12/14)(DI) (TUIJ) 1,148.00p +1.41%Glencore (GLEN) 257.35p +1.26%Carnival (CCL) 3,107.00p +1.21%Pearson (PSON) 1,336.00p +1.14%FallersMorrison (Wm) Supermarkets (MRW) 186.50p -6.05%Johnson Matthey (JMAT) 3,347.00p -4.29%Standard Chartered (STAN) 907.90p -3.59%Hargreaves Lansdown (HL.) 977.50p -2.54%Sage Group (SGE) 472.00p -2.48%Babcock International Group (BAB) 987.00p -2.47%Sainsbury (J) (SBRY) 263.90p -2.37%InterContinental Hotels Group (IHG) 2,671.00p -1.95%Antofagasta (ANTO) 680.50p -1.87%Tullow Oil (TLW) 363.80p -1.70%