Index: lucene/highlighter/src/java/org/apache/lucene/search/postingshighlight/PassageScorer.java
===================================================================
--- lucene/highlighter/src/java/org/apache/lucene/search/postingshighlight/PassageScorer.java	(revision 1455676)
+++ lucene/highlighter/src/java/org/apache/lucene/search/postingshighlight/PassageScorer.java	(working copy)
@@ -30,15 +30,37 @@
   // TODO: this formula is completely made up. It might not provide relevant snippets!
   
   /** BM25 k1 parameter, controls term frequency normalization */
-  public static final float k1 = 1.2f;
+  final float k1;
   /** BM25 b parameter, controls length normalization. */
-  public static final float b = 0.75f;
+  final float b;
+  /** A pivot used for length normalization. */
+  final float pivot;
   
   /**
-   * A pivot used for length normalization.
-   * The default value is the typical average English sentence length.
+   * Creates PassageScorer with these default values:
+   * <ul>
+   *   <li>{@code k1 = 1.2},
+   *   <li>{@code b = 0.75}.
+   *   <li>{@code pivot = 87}
+   * </ul>
    */
-  public static final float pivot = 87f;
+  public PassageScorer() {
+    // 1.2 and 0.75 are well-known bm25 defaults (but maybe not the best here) ?
+    // 87 is typical average english sentence length.
+    this(1.2f, 0.75f, 87f);
+  }
+  
+  /**
+   * Creates PassageScorer with specified scoring parameters
+   * @param k1 Controls non-linear term frequency normalization (saturation).
+   * @param b Controls to what degree passage length normalizes tf values.
+   * @param pivot Pivot value for length normalization (some rough idea of average sentence length in characters).
+   */
+  public PassageScorer(float k1, float b, float pivot) {
+    this.k1 = k1;
+    this.b = b;
+    this.pivot = pivot;
+  }
     
   /**
    * Computes term importance, given its in-document statistics.
Index: solr/core/src/java/org/apache/solr/highlight/PostingsSolrHighlighter.java
===================================================================
--- solr/core/src/java/org/apache/solr/highlight/PostingsSolrHighlighter.java	(revision 1455676)
+++ solr/core/src/java/org/apache/solr/highlight/PostingsSolrHighlighter.java	(working copy)
@@ -55,6 +55,9 @@
  *                      preTag="&amp;lt;em&amp;gt;"
  *                      postTag="&amp;lt;/em&amp;gt;"
  *                      ellipsis="... "
+ *                      k1="1.2"
+ *                      b="0.75"
+ *                      pivot="87"
  *                      maxLength=10000/&gt;
  *   &lt;/searchComponent&gt;
  * </pre>
@@ -78,8 +81,24 @@
   public void init(PluginInfo info) {
     Map<String,String> attributes = info.attributes;
     BreakIterator breakIterator = BreakIterator.getSentenceInstance(Locale.ROOT);
-    PassageScorer scorer = new PassageScorer();
     
+    // scorer parameters: k1/b/pivot
+    String k1 = attributes.get("k1");
+    if (k1 == null) {
+      k1 = "1.2";
+    }
+    
+    String b = attributes.get("b");
+    if (b == null) {
+      b = "0.75";
+    }
+    
+    String pivot = attributes.get("pivot");
+    if (pivot == null) {
+      pivot = "87";
+    }
+    PassageScorer scorer = new PassageScorer(Float.parseFloat(k1), Float.parseFloat(b), Float.parseFloat(pivot));
+    
     // formatter parameters: preTag/postTag/ellipsis
     String preTag = attributes.get("preTag");
     if (preTag == null) {