You will be presented with the full text of a science research paper. Please write an abstract for this paper. Your response should include the abstract and no additional text.

Paper text:
the na61/shine experiment and its predecessor na49 at the cern sps study an important region of the phase diagram of strongly interacting matter . the statistical model of the early stage ( smes ) of nucleus - nucleus collisions @xcite predicted the energy threshold for deconfinement at low sps energies .
several structures in the excitation functions were expected within the smes : a kink in the pion yield per participant nucleon ( change of slope due to increased entropy production as a consequence of the activation of partonic degrees of freedom ) , a sharp peak ( horn ) in the strangeness to entropy ratio , and a step in the inverse slope parameter of transverse mass spectra ( constant temperature and pressure in a mixed phase ) .
these signatures were observed in central pb+pb collisions by na49 around @xmath1  gev  @xcite .
fluctuation analysis may provide additional evidence of the onset of deconfinement . moreover , theoretical considerations suggest a critical point ( cp ) of strongly interacting matter which may be observable in the sps energy range according to most lattice qcd calculations  @xcite .
fluctuations and correlations are basic tools to study this phenomenon .
enlarged fluctuations are expected close to the critical point . in nucleus - nucleus collisions
a maximum of fluctuations is expected when freeze - out happens near the cp .
na61/shine is a fixed target experiment located in the north area of cern . _
shine _ stands for * s*ps * h*eavy * i*on and * n*eutrino * e*xperiment .
it was approved in 2007 .
na61 greatly profits from the long development of the cern particle sources and the accelerator chain as well as the h2 beam line of the cern north area .
the latter has recently been modified to also serve as a fragment separator as needed to produce the be beam for na61 .
na61/shine inherited the basic components from its predecessor , the na49 experiment , and added important upgrades . the na61 setup is presented on fig .  [ na61setup ]  ( left ) .
the detector consists of five time - projection chambers .
three of them ( vtpc-1 , vtpc-2  and  gap - tpc ) are located in a magnetic field .
two others ( mtpc - l and mtpc - r ) are located downstream of the vtpcs .
the tpcs are supplemented by three time - of - flight walls located behind the mtpcs .
this setup allows for good particle identification and momentum resolution.the na61@xmath0shine goal is to measure hadron production in p+p , p+a , h+a and a+a interactions at the sps energies , in order to :    * obtain precise data on hadron production ( spectra ) in p+c interactions at 31 gev@xmath0c for the t2k experiment for precisely computing the initial neutrino flux from the t2k target at j - parc , * perform reference measurements of @xmath2+c and p+p interactions for cosmic - ray physics ( pierre - auger and kascade experiments ) for improving air shower simulations , * search for the critical point of strongly interacting matter , * study the properties of the onset of deconfinement , * study of high @xmath3 particle production ( energy dependence of @xmath4 ) .    in order to study properties of the onset of deconfinement and
search for the critical point na61 performs for the first time in history a two dimensional scan in system size and energy
. already gathered systems and energies as well as planned measurements are presented in fig .
[ na61setup ] ( right ) in the phase diagram of temperature and baryo - chemical potential .
the following results were obtained from p+p data collected in 2009 by na61/shine at @xmath5 gev . event and track cuts
were chosen to select only inelastic interactions and charged particles produced directly in the interactions or via strong and electromagnetic decays .
results on single - particle spectra for @xmath6 mesons are obtained using two methods .
first , by the @xmath7 method which is based on the fact that the majority of negatively charged particles are @xmath6 mesons .
the contribution of other particles was estimated and subtracted using the venus and epos models .
second , by the @xmath8 method which uses information on particle energy loss in the tpc gas in the relativistic rise region to identify particles .
results from both methods are corrected for feed - down from weak decays and detector effects using simulations .
out - of - target interactions are subtracted using events recorded with the empty liquid hydrogen target .
transverse mass spectra of @xmath6 in p+p interactions at @xmath9  gev are presented in fig .
[ mt ] ( left ) . for all energies @xmath10 spectra are approximately exponential .
the ratio of na49 spectra for central pb+pb collisions @xcite to those of na61 for p+p interactions , both normalized to unity , is shown in fig .
[ mt ] ( right ) .
the concave shape of the ratio seems to be energy independent .
mesons in inelastic p+p interactions at @xmath9  gev ( left ) compared to central pb+pb data of na49 ( right ) .
statistical errors are indicated by vertical bars and systematic uncertainties by colored bands.,title="fig:",width=220 ]   mesons in inelastic p+p interactions at @xmath9  gev ( left ) compared to central pb+pb data of na49 ( right ) .
statistical errors are indicated by vertical bars and systematic uncertainties by colored bands.,title="fig:",width=220 ]     mesons in inelastic p+p interactions at @xmath9 gev ( left ) and mean pion multiplicity per wounded nucleon as a function of the fermi energy measure @xmath11 ( right).,title="fig:",width=230 ]   mesons in inelastic p+p interactions at @xmath9 gev ( left ) and mean pion multiplicity per wounded nucleon as a function of the fermi energy measure @xmath11 ( right).,title="fig:",width=230 ]    rapidity spectra of @xmath6 mesons in inelastic p+p interactions at @xmath9  gev are presented in fig .
[ kink ] ( left ) .
an excellent fit at all energies is obtained by the sum of two symmetrically displaced gaussian functions from which the mean @xmath6 multiplicity was derived.the mean yield of pions ( @xmath12 ) per wounded nucleon ( fig .
[ kink ] ( right ) ) was calculated using phenomenological isospin factors @xcite .
na61/shine measurements are in agreement with the world data . the mean multiplicity in central pb+pb rises faster than in p+p collisions with a crossover at about @xmath13  gev .
the precision of the data allows for a detailed study of the onset of deconfinement.rapidity spectra of @xmath6 , @xmath14 , @xmath15 mesons and protons produced in inelastic p+p interactions at @xmath16  gev are presented in fig .
[ szymon ] .
the spectra are compared with the corresponding na49 results @xcite spectra ] as well as with the epos model @xcite .
the experimental data agree for all particle types , between both analysis methods and na61 and na49 .
the epos model shows significant deviations from the data for @xmath15 mesons and protons .    , @xmath14 , @xmath15 mesons and protons in inelastic p+p interactions at 17.3 gev .
the na61 results are compared with the corresponding na49 data and predictions of the epos model.,title="fig:",width=211 ] , @xmath14 , @xmath15 mesons and protons in inelastic p+p interactions at 17.3 gev .
the na61 results are compared with the corresponding na49 data and predictions of the epos model.,title="fig:",width=211 ] , @xmath14 , @xmath15 mesons and protons in inelastic p+p interactions at 17.3 gev .
the na61 results are compared with the corresponding na49 data and predictions of the epos model.,title="fig:",width=211 ] , @xmath14 , @xmath15 mesons and protons in inelastic p+p interactions at 17.3 gev .
the na61 results are compared with the corresponding na49 data and predictions of the epos model.,title="fig:",width=211 ]      particle identification for the chemical fluctuation analysis is based on energy loss measurements in the relativistic rise region .
it does not allow unique identification of hadrons .
the mean hadron multiplicities are obtained by fitting a sum of response functions for each particle type to the measured inclusive de@xmath0dx distributions in narrow phase space bins . in order to analyze fluctuations of identified hadrons in p+p interactions of na61/shine , as well as pb+pb collisions of
na49 a new approach , the so - called identity method @xcite , was used .
it allows to obtain second and third moments ( pure and mixed ) of identified particle multiplicity distributions corrected for the effect of imprecise event - by - event particle identification .
fluctuation measure as a function of collision energy for p+p ( na61 ) and central pb+pb ( na49 ) collisions ( right ) .
the p+p data are compared with the epos model predictions.,title="fig:",width=201 ]   fluctuation measure as a function of collision energy for p+p ( na61 ) and central pb+pb ( na49 ) collisions ( right ) .
the p+p data are compared with the epos model predictions.,title="fig:",width=211 ]    two quantities , scaled variance @xmath17 of the multiplicity distribution and the two - particle measure @xmath18 , were chosen for the chemical fluctuation analysis .
the scaled variance is defined as : @xmath19 where @xmath20 and @xmath21 are the mean multiplicity and second moment of the multiplicity distribution of particles of type _
i _ , respectively.the scaled variance is an intensive measure @xcite i.e. it is independent of the number of wounded nucleons in the wounded nucleon model or volume in the grand canonical ensemble but it depends on their fluctuations .
the last feature makes it difficult to compare p+p interactions with nucleus - nucleus collisions . for the poisson distribution @xmath22.figure [ chemfluct ] ( right )
shows the scaled variance for @xmath23 , @xmath24 and @xmath25 as a function of collision energy .
results refer to the na61 acceptance for chemical fluctuation analysis @xcite.the scaled variance for all studied hadron types increases with increasing collision energy .
the trend as well as the magnitude of the effect is well reproduced by the epos model .
as pions are the most abundant particles their fluctuations should be dominated by the kno scaling @xcite .
it yields a linear increase of the scaled variance with mean multiplicity of charged particles . in na61
this trend is modified by the limited detector acceptance .
values of @xmath26 for all energies are close to or above one .
this is most probably caused by strangeness conservation which leads to a correlation between the production of @xmath27 and @xmath15 mesons .
again the effect is weakened by the limited acceptance . to
the contrary baryon number conservation seems to suppress proton fluctuations .
this is because the proton multiplicity is mostly given by the two initial protons as production of proton - antiproton pairs is strongly suppressed by their large masses .
this suppression effect is again weakened by the limited acceptance and it is expected to decrease with increasing energy . in order to compare results for p+p and central pb+pb collisions , the strongly intensive measure @xmath18 @xcite defined for two hadron types , i and j , was chosen .
it is defined as : @xmath28 , \ ] ] where @xmath29 / < n_{i}+n_{j}>$ ] . as a strongly intensive measure
, @xmath18 is not only independent of number of wounded nucleons or volume but also of their fluctuations.figure [ chemfluct ] shows the energy dependence of @xmath18 for combinations of two hadron types : @xmath30 , @xmath31 and @xmath32
. when no inter - particle correlations are present @xmath33.for @xmath31 and @xmath34 @xmath18 increases with increasing energy . for @xmath35
there is a minimum between @xmath36 and @xmath37 gev .
a similar but weaker effect is visible in pb+pb interactions .
it also appears in the epos model .
the increase of @xmath38 for p+p interactions is not observed in pb+pb collisions .
@xmath39 shows a clear difference between results for p+p , which increase with increasing energy , and pb+pb which decrease with increasing energy
. both dependencies cross zero at the same energy @xmath40 gev .
the na61/shine experiment successfully started the planned 2d energy - system size scan with p+p interactions .
the results are needed as reference for the onset of deconfinement study and the search for the critical point.the @xmath10 spectra of @xmath6 mesons are approximately exponential .
the comparison to pb+pb interactions shows noticeable differences for the lowest and highest @xmath10 values which seem to be energy independent .
a sum of two gaussian functions is required to fit the rapidity spectra of @xmath6.the energy dependence of the mean pion multiplicity per wounded nucleon from na61/shine agrees well with the previously established trend.fluctuations of identified @xmath2 , @xmath41 and protons in inelastic p+p interactions are well described by the epos model .
conservation laws seem to play an important role in fluctuations of hadron multiplicities .
comparison with data on central pb+pb collisions measured by na49 shows large differences between p+p and pb+pb in terms of fluctuations which are most pronounced for @xmath34 fluctuations .
m. gadzicki and m. i. gorenstein , acta  phys .
b * 30 * , 2705 ( 1999 ) na49 coll .
c * 77 * , 024903 ( 2008 ) z. fodor and s. d. katz , jhep * 0404 * , 050 ( 2004 ) na49 coll .
c * 66 * , 054902 ( 2002 ) na49 coll .
, phys .  rev .
c * 77 * , 024903 ( 2008 ) a.i .
golokhvastov , phys .  atom .
nucl .  * 64 * , 1841 ( 2001 ) na49 coll . ,
j. c * 68 * , 1 - 73 ( 2010 ) na49 coll . ,
j. c * 65 * , 9 - 63 ( 2010 ) na49 coll .
j. c * 45 * ( 2006 )
the na61/shine experiment aims to discover the critical point of strongly interacting matter and study properties of the onset of deconfinement 
 . it also performs precise hadron production measurements for the neutrino and cosmic rays experiments . 
 these goals are being achieved by measurements of hadron production properties in nucleus - nucleus , proton - proton and proton@xmath0pion - nucleus interactions as a function of collision energy and size of the colliding nuclei . 
 this contribution presents preliminary results from the na61 ion program on single - particle spectra and identified particle multiplicity fluctuations in p+p interactions at the cern sps . 
 comparisons with results from p+p and pb+pb collisions obtained by the na49 experiment are shown .