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for the general case of @xmath1 transition into a combination of @xmath27 ( @xmath28 ) and @xmath29 ( @xmath30 ) states one can write the sk , sno cc and sno nc rates as r^el_sk & = & f_b p_ee + f_b r p_ea , [ two ] + r^cc_sno & = & f_b p_ee , [ three ] + r^nc_sno & = & f_b ( p_ee + p_ea ) , [ four ] where @xmath16 and @xmath31 denote the probabilities folded with the detector response function @xcite and averaged over energy . to extract a model independent bound on @xmath16 one has to ensure an equality of the response functions which amounts to slight adjustment of the sk threshold energy and the rate @xcite . our approach is slightly different . we treat @xmath16 to be effectively energy independent . the sk spectrum data indicates a flat probability down to 5 mev @xcite . this is corroborated by sno @xcite which now has a threshold of 5 mev for kinetic energy of the observed electron . hence we consider this assumption as justified and expect the results to be insensitive to the differences in the response functions . it should be noted here that in cotrast to the sno cc events their nc events correspond to a neutrino energy threshold of 2.2 mev . however it is clear from eq . ( 5 ) that for a @xmath1 to @xmath28 transition there is no reason to expect any energy dependence in @xmath32 . on the other hand for the general case of @xmath1 transition into a combination of @xmath28 and @xmath30 our approach effectively assumes @xmath33 to be energy independent down to 2.2 mev . a comparison of the current values @xmath19 with @xmath32 is shown in fig . 1 . it constitutes a 5.3@xmath34 signal for transition to a state containing an active neutrino component or alternatively a 5.3@xmath34 signal against a pure sterile solution . next we consider the general case where @xmath1 goes to a mixed state = @xmath35 . then one can write @xmath36 ) . substituting this in the equations ( [ two ] ) and ( [ four ] ) and eliminating @xmath16 using equation ( [ three ] ) one gets the following set of equations for @xmath24 and @xmath37 @xcite ^2(f_b - r^cc_sno ) & = & ( r^el_sk - r^cc_snc)/r , [ five ] + ^2(f_b - r^cc_sno ) & = & r^nc_sno - r^cc_sno . [ six ] we treat @xmath37 as a model parameter . and for different input values of @xmath37 we determine the central value and the @xmath38 and @xmath39 ranges of @xmath24 by taking a weighted average of the equations ( [ five ] ) and ( [ six ] ) . the corresponding curves are presented in fig . 2 . combining the 2 @xmath34 lower limit of @xmath24 from this fit with the @xmath39 upper limit from the ssm ( vertical lines ) gives a lower limit of @xmath37 @xmath40 0.45 i.e. the probability of the active component is @xmath40 45% . note that there is no upper limit on this quantity - i.e. the data is perfectly compatible with @xmath1 transition into purely active neutrinos .    assuming transition into purely active neutrinos ( @xmath41 ) we show in fig . 3 the @xmath38 and @xmath39 contours in the @xmath42 plane from the combinations sk+snocc and sk+snocc+snonc . the inclusion of the nc rate narrows down the ranges of @xmath24 and @xmath16 . the error in @xmath24 after the inclusion of nc data is about half the size of the corresponding error from ssm as is seen from fig . in this section we present the results of our @xmath43 analysis of solar neutrino rates and sk spectrum data in the framework of two flavour oscillation of @xmath1 to an active flavour . we use the standard techniques described in our earlier papers @xcite excepting for the fact that instead of the quantities @xmath44 and @xmath19 we now fit the ratios @xmath20 and @xmath21 . the @xmath0 flux normalisation gets cancelled from these ratios and the analysis becomes independent of the large ( 16 - 20% ) ssm uncertainty associated with this . we include in our global analyses the 1496 day sk zenith angle spectra @xcite . since we use both sk rate and sk spectrum data we keep a free normalisation factor for the sk spectrum . this amounts to taking the information on total rates from the sk rates data and the information of the spectral shape from the sk spectrum data . the sno cc and nc rates have a large anticorrelation . we have taken into account this correlation between the measured sno rates in our global analyses . further details of this fitting method can be found in @xcite . in table 2 we present the best - fit parameters , @xmath45 and goodness of fit ( gof ) . the best - fit comes in the high(lma ) region as before @xcite . however as is seen from fig . 4a the incorporation of the nc data narrows down the allowed regions , and in particular the low region becomes much smaller . we have also performed an alternative @xmath43 fit to the rates of table 1 @xcite along with the 1496 day sk spectra @xcite , keeping @xmath24 as a free parameter . even though we allow @xmath24 to vary freely the nc data serves to control @xmath24 within a range determined by its error . as we see from table 2 and fig . 4b the results of this fit are very similar to the previous case . the best fit comes from the high(lma ) region , while no allowed region is obtained for the low solution at the 99% cl level . maximal mixing is seen to be disallowed at the @xmath3 level . to illustrate the impact of the nc rate on the oscillation solutions we have repeated the free @xmath24 fit without this rate . the results are shown in fig 4c . evidently the nc data plays a pivotal role in constraining the oscillation solutions , particularly in the low / qvo region , which is allowed only at the @xmath3 level . it puts an upper bound on the @xmath46 in the lma region and rules out maximal mixing . the first sno nc data constitutes a 5.3@xmath34 signal for transition into a state containing an active neutrino component . the inclusion of this data puts much tighter constraints on @xmath24 and @xmath16 from a model independent analysis involving active neutrinos as compared to the sno cc / sk combination . in this paper we have discussed two useful strategies , of incorporating the nc data in the global @xmath43 analysis of rates and spectrum data , by which one can avoid the large @xmath0 flux uncertainty from the ssm . + @xmath47 we fit the ratios of the sk elastic and sno cc rates w.r.t the nc rate , from which the @xmath24 cancels out . + @xmath47 we fit the rates by keeping @xmath24 as a free parameter , where the inclusion of the sno nc rate (= @xmath24 ) serves to control this parameter . both the analyses give very similar results . they clearly favour the high(lma ) solution , while a limited region of the low solution is also acceptable at the @xmath3 level . the maximal mixing solution is disfavoured at the @xmath3 level . as more data accumulate one expects a substantial reduction in the error bar of the sno nc rate , resulting in further tightening of the allowed regions of neutrino mass and mixing . +   + _ note added _ : the paper @xcite appeared on the net after completion of our work . in the region of overlap our results agree with theirs as well as with the updated version of @xcite . it may be added here that the sno cc and nc rates given in table 1 are obtained assuming undistorted energy spectra above 5 mev , which for transitions to active neutrinos has good empirical justification as mentioned above . we thank prof . mark chen of sno collaboration for communication on this point . a. bandyopadhyay , s. choubey , s. goswami and k. kar , phys . lett . * b519 * , 83 ( 2001 ) ; s. choubey , s. goswami , k. kar , h.m . antia and s.m . chitre , phys . rev . * d64 * , 113001 ( 2001 ) ; s. choubey , s. goswami and d.p . roy , phys . rev . * d65 * , 073001 ( 2002 ) ; a. bandyopadhyay , s. choubey , s. goswami and k. kar , phys . rev . * d65 * , 073031 ( 2002 ) . fogli , e. lisi , d. montanino , a. palazzo , phys . rev . * d64 * , 093007 ( 2001 ) ; j.n . bahcall , m.c . gonzalez - garcia , c. pana - garay , jhep * 0108 * , 014 ( 2001 ) ; p.i . krastev and a.yu . smirnov , e - print archive : hep - ph/0108177 ; m.v . garzelli and c. giunti , jhep * 0112 * , 017 ( 2001 ) . j. n. abduratshitov et al . , sage collaboration , astro - ph/0204245 ; w. hampel _ et al . , _ gallex collaboration , phys . lett . * b447 * , 127 ( 1999 ) ; m. altman _ et al . , _ gno collaboration , phys . lett . * b490 * , 16 ( 2000 ) ; e. belloti , talk at gran sasso national laboratories , may 17 , 2002 ; t. kirsten , talk at neutrino 2002 , munich .            . the observed solar neutrino rates relative to the @xmath49 predictions ( bp2000 ) are shown along with their compositions for different experiments . for the @xmath50 experiment the @xmath1 contribution to the rate @xmath51 is shown in parantheses assuming @xmath52 transition . in the combined ga rate we have included the latest data from sage and gno . [ cols="^,^,^ " , ]
we perform model independent and model dependent analyses of solar neutrino data including the neutral current event rate from sno . 
 the inclusion of the first sno nc data in the model independent analysis determines the allowed ranges of @xmath0 flux normalisation and the @xmath1 survival probability more precisely than what was possible from the sk and sno cc combination . 
 we perform global @xmath2 oscillation analyses of solar neutrino data using the nc rate instead of the ssm prediction for the @xmath0 flux , in view of the large uncertainty in the latter . 
 the lma gives the best solution , while the low solution is allowed only at the @xmath3 level . 
 * implications of the first neutral current data from sno for solar neutrino oscillation * abhijit bandyopadhyay@xmath4 , sandhya choubey@xmath5 , srubabati goswami@xmath6 , d.p . 
 roy@xmath7 @xmath4saha institute of nuclear physics , bidhannagar , kolkata 700 064 , india + @xmath5 department of physics and astronomy , university of southampton , highfield , southampton s017 1bj , uk + @xmath8 harish - chandra research institute , chhatnag road , jhusi , allahabad - 211 - 019 , india @xmath9tata institute of fundamental research , homi bhabha road , mumbai 400 005 , india + @xmath10physics department , university of california , riverside , ca 92521,usa    the neutral current results from the sudbury neutrino observatory measures for the first time the total flux of @xmath0 neutrinos coming from the sun @xcite . in a recent paper @xcite we had examined the role of the anticipated nc data from sno in enhancing our understanding of the solar neutrino problem . 
 the sno nc rate can be expressed in terms of sno cc and sk elastic scattering rates as @xcite r^nc_sno = r^cc_sno + ( r^el_sk - r^cc_sno)/r , [ one ] where @xmath11 for a threshold energy of 5 mev ( including the detector resolutions and the radiative corrections to @xmath12 scattering cross - sections ) . 
 all the rates are defined with respect to the bbp2000 standard solar model ( ssm ) @xcite . 
 we showed in @xcite that because sno has a greater sensitivity to the nc scattering rate as compared to sk , the sno nc measurement will be more precise and hence incorporation of this can be more predictive than the sno cc and sk combination . 
 we took three representative nc rates  @xmath13 = 0.8,1.0 and 1.2 ( @xmath14 ) and showed that    1 .   for a general transition of @xmath1 into a mixture of active and sterile neutrinos the size of the sterile component 
 can be better constrained than before . 
 2 .   for transition to a purely active neutrino the @xmath15 neutrino flux normalisation and the survival probability @xmath16 
 are determined more precisely . 
 3 . 
 we had also performed global two flavour oscillation analysis of the solar neutrino data for the @xmath17 case , where instead of @xmath18 and @xmath19 we used the quantities @xmath20 and @xmath21 . 
 these ratios are independent of the @xmath22 flux normalisation and hence of the ssm uncertainty . 
 we showed that use of these ratios can result in drastic reduction of the allowed parameter regions specially in the low - qvo area depending on the value of the nc rate . 
 we now have the actual experimental result r^nc_sno = 1.01 0.12 while eq . 
 ( [ one ] ) gives @xmath23 . 
 thus in 306 live days ( 577 days ) the sno nc measurement has achieved a precision , which is already better than that obtained from the sk and sno cc combination . 
 this paper follows closely the analysis that we have done in @xcite but incorporating the actual data . 
 in addition we also perform an alternative global analysis for @xmath17 oscillation by letting the @xmath0 normalisation factor @xmath24 vary freely , where the inclusion of @xmath25 in the fit serves to control this parameter . 
 as we shall see below the two methods of global analysis give very similar results . 
 in section 1 we discuss the constraints on the electron neutrino survival probability , the @xmath0 normalisation factor @xmath24 and the fraction of sterile component without assuming any particular model for the probabilities . in section 2 
 we perform the global analyses assuming two flavour @xmath26 oscillation .